I have lots of friends like that. You will ask them if they want to meet up, and they say they will, but then they decide they have a better offer and cancel, which makes me feel insignificant to be honest. I've tried raising the point with them, but all it ever turns into is them accusing me of being selfish, and somehow, I always end up as the one apologising.
I have come to the conclusion that the best thing to do is grit your teeth, bear it, and carry on being a happy smiley person. It won't go un-noticed by other people that you go out of your way for your friends and that you're nice to everyone. It can be a pain in the butt, but stick with it!