Why do girls approach me or give attention then throw me off the cliff .....?

When Random girls approach me first for conversation OR if I meet them and know for a short while; I ask them a few basic questions about them.

After that I start to talk topics such as Ethics, Spirituality, Society, Science and spill my opinions on it and they listen attentively for a good 10 minutes or so. They literally look into my eyes and clearly listen well.

After conversing on those topics I resume back to asking some basic questions.

That's when the girls say." Nice to meet u" , " Got to go" or even sometimes casually mention their boyfriend.

They also seem to stare at me as they leave as well and play with their hair.

So I am wondering if i am doing anything wrong? Do they hate me or like me??

Thanks:)