Why do guys like plain girls? Do they feel more comfortable with them or something?

Perhaps he's scared or intimidated by the really pretty girls. Pretty girls are purely confident especially when they know they're pretty, and can take advantage of men. I had a really hot girlfriend and I felt as if she had me on the leash cause I was scared that she could leave me any time. I didn't give myself that confidence. However, I've changed and I became a very confident man, where we both think we're great looking people =).