But like I said, I think we're wired differently...so our natural impulses aren't always in line with one another.
How many monogamous gay men do you know? There definitely are a lot of them out there, but I would offer that a majority of gay men lead lives that include numerous sexual partners. To me, this is just further evidence that most men (of any sexual orientation), given the chance to have as much sex with as many different people as they can, would jump at it.
Sure, they might risk ruining the relationship they're in...but whatever their reason (poor impulse control, bored by monogamy, etc.) a lot of guys go for it.

"Marriage is a wonderful institution...but who wants to live in an institution?" -- Groucho Marx