Gay dudes are attracted to other dudes, and since most dudes like sex, making a connection can be pretty easy. Evolutionary theory says that men are wired to sow their seeds as widely as possible, so being male means being wired for promiscuity, something true for all men, straight and gay. So two men together can be all gas pedal and no brake.
Women, on the other hand, may love sex just as much as men, but are more likely to take other factors into consideration. Before the invention of birth control in a pill, for example, women could be left pregnant and caring for a child. So traditionally, women suffered more dramatically from poor sexual choices than men. In male-female relations, then, it is often men who are pushing on the gas pedal, and women in charge of the brakes.
The problem is that the entire milieu in which gay men’s moral and sexual socialization takes place is so deeply compromised, so bereft of sustainable meaning and protracted monogamous commitment, that marriage in the traditional sense (which is what I believe gay men are trying to achieve in their lives) will be impossible to realize.