Why do women get mad at me when i do something nice?

This has actually happened quite a bit now, whenever i see that someone, man or women, needs help carrying something, or just in general, i try to help them. I hold open doors and do polite things also. Some of the women I have come across actually get mad at me for doing this! They exclaim, "I can do it myself, I don't need your help" or something like that. I also hear many girls complain that guys aren't nice or thoughtful anymore, but when they do stuff like this, is it their fault?I am all for equality, but i think this is going too far.