Easier for girls to be gay than guys. Don't worry, it's not for any good reasons.
Note: The following are things society/random individuals in society believe. I am not claiming they are true in any interesting sense. I am also not talking about 'lipstick lesbians' or anything like that, but rather people who actually screw.
1) Penises are scary. They can get ladies preggers, they ooze stuff, the guy owning/operating it might be mean or something. If you bang a dude, you're a slut or there's some expectation of a relationship. And seriously, did you just have pre-marital sex? You're totally going to ho-bag hell.
Girls, on the other hand, don't have scary dicks on the whole. You can be 'experimenting' (horny), it can be emotional, whiny and end soon after and it's okay, etc. And when all is said and done, you can say, "it was just a phase, I'm totally straight now," and nobody bats an eyelash. For gay guys, penises are exactly as scary as for girls and you generally have to commit to some level of 'being a slut' as far as society is concerned. And once you do a dude as a guy, you're a gay. Forever.
2) Misogyny. Women are lamer than dudes, right? So why should a lady bring some awesome dude down to her level by having sex with him? Exactly: no good reason. So if you're gay enough to like ladies at all and are yourself a lady, the kindest thing you can do for society is to have sex with only ladies.
3) The dull distinction between the characters of men and women. Men are loners and it's gay to hang out with other men. Women love hanging out with women and that's how straight girls roll. And if some hanky-panky happens when you're with your friends, what's the big deal?
4) Women are just extra-wussy gay men already, with the smallest dicks evar and surprisingly big moobs (sometimes). Gay guys love hanging out with them and emulating them, straight guys can't handle their womanly ways. And if society already basically views them as gay guys, why shouldn't they have gay sex too?
5) Everybody is attracted to some degree or another to any human they have any interest at all in. As in: Jeff seems cool, I should talk to him. Or literally any feeling about your teachers at school, or that annoying girl who talks too much. That is actually what your interest in somebody MEANS: that you want to have sex with them in some way or another. The result is that, practically, men are probably exactly as gay as women are, but it's easier for women to act on their homosexual desires for the above reasons.