Same. I guarantee that when I was younger my hairstylist was making more than me. My best friend, who went to the same stylist, and myself would always joke about it. She was driving a brand new CLK convertible, and had a fabulous wardrobe and shoes. We tipped her well because she was fantastic, not because we thought she was hurting for money. I tipped her assistant too... even though my hair cut color etc. were completely overpriced.
I think it just comes back to what is customary, and what is the social norm. There are certain positions that are normally tipped positions, and there are others that are not. It's really just a simple as that.