Why are there so many popular songs idealizing women who don't know they are beautiful?

I've noticed that there are lots of pop songs that glorify women who don't know they're physically attractive. Here's an example: "You don't know you're beautiful, That's what makes you beautiful." Does this indicate something about what men want? Do they want a woman who doesn't know her own value? Or does this indicate something about how most women have body image issues?