Lesbians and taken girls like me enough to talk, but single girls avoid me. Why is this?

Perhaps you are the ''nice guy''. I've learnt few things about relationships over the last 5 years. Girls tend to go for those ones who are confident, those ones who don't accept demands from girls, charming ones. It's kinda hard answer a question directly based on a majority. I think girls generally tend to like those ones who show moderate attention because if you show too much attention it suggest insecurity. Sometimes you just need be the leader and take decision by yourself, because girls generally don't avoid guys based on their way to speak or anything alike. As a matter of fact, I used to care too much about girls, then i learnt that i would always stick in their friendzone or even be those kind of friend who usually tend to give advices when all you want is date the girl in question. Just be honest with yourself, confident and sometimes leader whenever you need be, then sooner or later you will eventually find a girl who likes you the way you are. In fact, there are no many ways to describe human behaviours in 2 or 3 sentences, it's all about personality and attraction as well.

Nevertheless, if you like the hardcore way to deal with the facts, then I suggest two books written by Robert Greene: The Art of Seduction and 48 laws of power.