Can someone explain this to me?

First I'm gonna start out by saying I DONT mean this in a negative or condescending way (I just really don't understand) so I'm hoping that you guys can clear this up for me. That being said, why do some girls that are lesbians date girls that look like men? Like wouldn't you be kind of bisexual then? Not lesbian? Idk. Again not meaning to offend so please don't take it that way. I'm just curious