Most Helpful Guy
You want to know the real reason why? Because they aren't attractive enough to get their dream guy. As long as they can't get their dream guy, they are hideous. Nobody else matters. Nothing else matters. If you tell a girl she's beautiful and she takes it lightely, SHES NOT TRYING TO IMPRESS YOUR ASS. She wants confirmation from guys she will actually screw with passion.
Not all girls are like this. I felt the need to add that last part so I can avoid at least 2 or 3 downvotes.