Do you tip the owner of the hair salon?
Barbers who own their own shops and cut men's hair deserve a tip as well.
My barber/shop owner could cut my hair in five minutes, but he stretches the job into a half hour affair, waving his arms erratically while telling lewd stories that keep me riveted to the chair, praying that he won't poke my eyes out with those long scissors. His talent for hair cutting is average, but he can tell a yarn that keeps me transfixed just long enough to over tip him.
My mom never tips. I'll leave something for whoever cut our hair when she's not looking. Or should I tell her? In fact, I can't remember one time I saw other people tip....
ETA: I've found the best tippers are people in service-type positions, who have had to work for tips themselves. They know how hard it is, and are generous in showing their appreciation for a thankless job.