...seriously? well, because women and men experience life very differently. being a woman is a lot more dangerous - you are simply too weak to defend yourself against most guys. so, you have to trust that they will treat you fairly before sleeping with them or starting a relationship, and if you're wrong, the consequences are terrible. men simply don't have to worry about consequences this severe - as a guy picking up girls, you never have to wonder if they will rape or abuse you.

remember that rape is still exceedingly common (1 in 3 women in the USA will be sexually abused at some point). women are just as sexual as guys, it's just much more dangerous (and socially unacceptable - slut-shaming, etc) for them to solicit sex. as for why anonymous dudes on the internet are so creepy, it's most likely a combination of the disinhibition anonymity gives you and the sexual deviance a boner gives you.