Other contributors have said "Do girls like to rub a guy?" is the same question as "Why do guys like to rub girls' feet?" If you believe that these are not asking the same thing and should be answered differently, click here
They feel it's sexy. They feel the girl enjoys it to the extent that she wants hime to do that for her. And besides it feel good when anyone wants to massage you in anyway! Haha.
They also like to because it makes them feel closer to you
Because they are soo beautyful. And relatively smaller than boys' feet and there are differences in their shapes. But I think some of girls like to show their feet too.
Not all guys like feet...
I'm sure I speak for millions of women when I say that a foot rub is always appreciated. However, I don't know of any women who admit being turned on by a foot rub, if that's what you mean.