Why do gays want to get married anyway? Don’t they know divorce is expensive?

Around the world, the marriage rate is falling. Statistics show that less and less people are getting married and more and more people are getting divorced. Fine time for the gay community to win marriage rights, isn’t it?  
I don’t think gay people know how good they have it. Until now, they’ve been able to get the milk for free without buying the cow. But it wasn’t good enough. They want the milk and they want the cow. And it looks like they will get what they prayed for especially now that the California feds have struck down Prop 8. But is this a good win? Or is it really a curse? Gays could be praying for a…big headache (Heterosexuals are figuring that out and are staying unmarried en masse!).
The right to marry is a huge win for the gay community but  is this best for them? Is it what they need? There are so many advantages to just having a domestic partnership. There are so many advantages to having the cow, getting the milk for free, but not owning the bloody thing. Know what I mean?
Look, if I may play devil’s advocate, it is widely known that men have a tougher time at fidelity than women. For whatever reason. The testosterone, whatever. Guys  just have a tougher time with being with just one person. This is true even in heterosexual relationships, btw.
So let’s say we have a gay couple who decide to get married–because they can. It’s not a huge over-generalization to say that there is a pretty good chance that at some point in that relationship, some one of them will cheat. And that’s fine. That is not the problem. Because it seems that infidelity is one of those things that a lot of gay couples “negotiate.” (Heck, this is true for some heterosexual couples as well).
The thing is, marriage changes everything. It does for heterosexuals and it will for homosexuals. Folks will cry up and down that marriage won’t change anything. But I beg to differ. The minute people marry the rules of engagement will change. All of a sudden, whereas they “negotiated” their infidelities when they were just “partners” who were not “married,” now, all of a sudden, expectations change; they want and expect their spouse to be faithful. They want that exclusivity. They become more possessive and territorial. They will demand monogamy under color of law, and when they don’t get it, when there is “adultery” then you are looking at a huge number of divorce cases hitting the courts’ dockets.
And there is going to be adultery. A lot of it.  And the jealous hissy fits are not even going to be funny when one of them strays.
The thing though, is that now that they are spouses and not just partners or not just lovers, there are property rights and interests that exist – with or without a partnership agreement or a prenup. Rights automatically exist. Marital property is created automatically once parties are married. So when a spouse gets ticked off because the other one cheated? For a lot of gay spouses this is really going to hurt their bottom line in divorce court. Because now, adultery is consequential. It has a dollar value. And the more affluent the transgressor, the more he or she will pay for their sins.
So my question is, why do that to themselves in the first place? Why buy the cow when they can have the milk for free given that divorce can be so…expensive?