Why are women so much SELECTIVE when it comes to being attracted to males from a scientifical point of view?

> Be me, homosexual man
> Waiting for my turn at the cashier
> Very handsome and well dressed young man in front of me. Cannot stop staring at him, I feel like melting
> Two girls behind me gossip about how ridiculous and funny the guy is

I don't understand. Why is there such a huge difference between how a woman and a gay man react to a decent looking male?