Why do you care for someone and they don't care for you?

Everyone likes different things. Sometimes you do like someone else, but your personality does not attract them, so they don't like you back. That's OK for both of you -- everyone has the right to like whoever they want to. It may be sad for a little while, but sometimes it can also have a happy ending if you keep being friendly to them and not get mad, they might decide they like you later on.