Why Is It Easier To Hook Up With Men?

I think generally (but in no way a definite) it is because many guys feel "cooler" when they get a girl. Something to brag about to friends. Also, yes they are "horny doggy dogs" as well.

Societal double standards chastise women for having sex, while praising men for it. Not to mention, women don't like the idea of being pregnant, even when they want kids they just want the kids. That said, since men can't get pregnant they're typically less reserved about it.