I have a "few" thoughts on this subject (
NATURALLY):
1) First, this is not a scientific poll and therefore we have to be very careful about drawing too many conclusions on what it means about mongers and marriage.
2) Even if it were more scientific or did somehow accurately reflect the percentages of mongers in various states of marriage, the polling method is still flawed as it relates to marriages in general. I'm not at all surprised to see the rate of divorce and/or never married to be significantly higher among a group of mongers than it would be in the general population.
3) What conclusions can be drawn from that fact are another question. There is a saying in research called "correlation does not imply causation". In this case, that means that just because those who engage in our somewhat unusual hobby also happen to have a higher rate of non-marriage or divorce, does not mean that the former caused the latter or even the other way around that our marriage status caused us to turn to mongering. It is just as possible some other factor not measured in this poll that we all share as mongers led us both to mongering AND to our marriage status, whatever it happens to be. Perhaps is is an affinity for greater sexual adventure or greater openness to unconventional behavior? Perhaps it is because we all share a certain cynicism about marriage? Who knows?
4) That 50% of marriages that end in divorce (among the general public) statistic that one so often hears ignores another number that might give it even greater significance. How many of the other 50% that don't end in divorce are truly happy? I'm sure many are but I'm also sure many aren't what we could really call successful marriages. People stay in bad marriages for a variety of reasons. Sometimes it is "for the Ch*ldren". Sometimes it is because, they see it as simpler or more politically or socially expedient than going through the pain of divorce (e.g. the Clintons). Add in those marriages to the 50% and the odds of a marriage working out in the longterm really become heavily stacked against you.
5) Society makes it real easy to get married. In some places you don't even need a blood test and all you have to do is show up at the courthouse (or for the Elvis Impersonator at the "Chapel of Love"). Society also heavily encourages marriage as an institution. Women were taught to dream about their marriage day ever since they were little girls. OTOH, society makes it comparatively hard to get divorced. It could be argued this is a good thing since it forces couples to try to work through their problems before resorting to disolving the marriage. IMHO, society has got this formula backwards. It should be harder to get married and easier to get divorced. One reason there are so many bad marriages that end in divorce is because the couples probably should never have been married to begin with. Maybe they got married when they were too young and were still developing emotionally and then one or both parties changed. Maybe they entered into marriage too frivolously without any serious consideration of what marriage really should entail. And once a couple is married and they encounter problems they should try to deal with them first and perhaps even go for counseling before turning to divorce but, once that stage is reached and other avenues have been exhausted, it, divorce, should not be made so difficult.
6) Staying in a bad marriage for the sake of the Ch*ldren is like pulling a bandaid off slowly. K*ds know what is going on. They can feel the friction. Often times it is better to pull that bandaid off quickly in order to get the pain over with, rather than dragging it out, so that everyone can just move on.
7) In the old days when the institution of marriage was first developed, people didn't live much longer than the dozen or so years it took to raise their Ch*ldren to the point they could become self-sufficient themselves. And don't fool yourself into believing all of those dozen or so years were so happy just because they didn't countenance divorce like they do today. It is also worth pointing out that probably more men ended up "mongering" in one way or another back in those days when they were not socially allowed to publicly leave their wives. IMHO, the whole idea of finding someone you could stay in love with for you whole life is completely unrealistic for most people when your whole life often means living into your 80's and 90's as it does today.

Marriages as an institution are designed mainly to protect the women and to help insure that the husband will stick around and do his part to help raise their Ch*ld. Traditionally, men have been the breadwinners while women have stayed home raising their K*ds. As such, men don't need the women so much as women needed men. Even today, when this equation has largely changed in the US, divorce laws are still heavily weighted in the woman's favor. Peenuptial agreements can ameliorate much of that problem by clarifying in advance what a divorce sttlement would be in advance were that to happen, but there are some restrictions on what can be put into a prenupt and many women (wisely so from their perspective) would refuse to sign such an agreement, ostensibly because it is unromantic but also because it is clearly not in their best interest.

Today, IMHO, given the widespread acceptance of extramarital sex and even couples living together before or outside of marriage and given the existence of archaic divorce laws, it makes little sense and provides little or no advantage for guys to get married in the first place. True, it does act as a sign of commitment and forces couples to work on the minor difficulties that all marriages face from time to time. But, IMHO, couples don't need a legally binding document to commit to each other when both sides know that legally binding document can be broken at some later date anyway (albeit with some difficulty). Couples can also commit to each without actually getting married. They can try to work through their problems BUT, if those problems become irreconcilable, they can also walk away.
9) The only exception to my paradigm above is when it comes to having and raising K*ds. And here I'm not talking about when you accidentally knock up your girlfriend and decide to get married because of that. But, if you are PLANNING to have K*ds with a woman, that undertaking should not be entered into lightly and should be seen as a longterm commitment of at least the 18-19 years it will be before that Ch*ld goes off to college. I said in #6 that it is better to get out of bad marriage than to stay in it "for the sake of the K*ds", but it is even better yet to have a stable marriage BEFORE you decide to have the K*ds so that you're more likely to have a solid and stable background for the whole period they're growing up.
10) Finally, of greater interest to everyone here, is the question of marriage and mongering. Does mongering break-up marriages or does it provide a relief valve that makes it possible for those marriages to continue on? I can't really say for sure since I fall into the never married category myself, but I do have "few" ideas (NATURALLY). I don't think you can really generalize here. In some cases, I think mongering is a symptom of an already bad marriage. In other cases, it is merely a somewhat innocent relief valve in an otherwise basically good marriage. But you have to ask yourself if it is really all that innocent why do you have to sneak around about it. An otherwise good marriage may be seriously damaged or destroyed if or when a wife finds out her husband has been sneaking around and going with hookers behond her back. In still other cases, which seems to tend to be the accepted norm among latino couples, the husband is expected to "cheat", have mistress(es) etc. and it is more or less seen as okay as long as the wife is not confronted with it or finds out. In other words, she more or less knows or suspects that "all men are dogs", but just don't shame her by failing to be discreet. The rare case is where a guy can openly hound-dog around with his wife's knowledge or tacit approval.