why do woman expect men to change?

I'm sure you are a nice guy like you said, but that is not grounds for a girl liking you. Perhaps the girls you have met and were interested in didn't like you because they didn't want to date at the time or felt that your personality wasn't matching with yours. This isn't a bad thing, it's just an issue with timing. You can meet a woman that likes you, and probably will like you for your personality rather than the sole fact that you are nice.

They just do. They think it's the right thing to do when actually they don't realize that is a red flag, if they're already trying to change them.

About the whole nice guy being turned down. Women look for something exciting, thrilling, sometimes daring in relationship than the usual everyday. They like bad boys because they find their confidence and braveness attractive. They also like how getting someone wasn't too easy.

Try chasing each other, do different things and get outta your comfortable zone, start being flirty, There's a lot of things you can do (:

Women marry med expecting them to change, men marry women expecting them not to change.

Women like men who are a challenge. Nice guys aren't a challenge, bad boys are. Women like the idea of taming a bad boy while men like the idea of having a woman who f$^ks like a porn star.