Guys, if you lose interest in someone but only want from them?

I'm obviously a girl...& I don't think you should have to go through any of that just to have with someone. Why are you wasting her time...doing nice things for her if you only want "one" thing from her. Do you have no feelings at all? She probably really likes you & she's probably thinking that this relationship could go pretty far...if only she knew that you were just playing her all along. Not a good way of trying to have with her If you're not really into her. Sorry. & hope i didn't sound to harsh. Just trying to be truthful.