The whole thing's basically a huge put-on. You can't 'act straight' any more than you can 'act gay'.
Statistics on the matter will always be inaccurate as long as being non-heterosexual carries any sort of stigma. You can't depend on honest answers in any study related to orientation.
A lot of gays are conditioned into insecurity and as a result, try to latch onto the hyper-masculine ideals that don't really exist in the world. In porn, this is played off of.
There are also plenty of them who are enchanted either by straight boys 'playing gay' (when in reality they're probably not so strictly straight), or by feeling like they're getting a glimpse at some sort of forbidden secret. The reality is that straight boys are just as pressured, on the whole, towards that same hyper-masculine nonsense.
In many cases it's 'the grass is greener on the other side' – it becomes alluring when they feel they're privy to something they'd otherwise never be able to witness...or at least, that's what they imagine.
I do think it's always troubling when one comes across these obsessive, often self-loathing types so fixated on playing pretend that they end up being just embarrassing and sad. There are people of all kinds, male and female, gay, straight, and everything else, that believe in these stereotypes. But what people don't often think about is that putting on a 'straight act' is often as embarrassing and insulting as the other way around. Funny thing, I was shocked the one time I can remember seeing it pointed out once on a show...Dante's Cove, of all things!!
