Why would a girl not play footsie with her boyfriend when it's important to him?

Playing footsie is a cool way of showing affection, especially if both are in bare feet. I don't understand why so many women wouldn't let their boyfriends do it with them. If they really like the guy, what's the problem? I know some girls have phobias but if it's really important to him, I would think she would make an exception. If not, then I guess she never really had feelings for him.