Another buff wearer here. Besides the advantages posted by others, it helps me to get my helmet ON. I have a ton of hair that if unruly, ends up getting all wound up in my helmet and actually hurting me. I've even had cases where the helmet didn't sit right due to my hair configuration and it hurt my forehead after a few minutes. A buff will tame all that for me.

It's also deliciously cool if soaked with water before putting it on in the summer.