Do you tip for haircuts?

My wife always does but I never have. At the most, it takes 15 minutes to cut my hair. The service I receive is fine but it's not like she shines my shoes and gives me a beer. I usually tip 10% for the wait staff at buffets and 20% and full serve restaurants. My reasoning for tipping them is they get paid next to nothing per hour and rely on tips. Everybody else who holds out a tip jar is making at least minimum wage as far as I know so I do not tip them. I just switched barbers (stylists?) because my longtime previous stylist decided it was time to be a stay at home mom. I went to the new one tonight. I am considering tipping her but have not decided for sure yet.

Anyway, I am mostly curious about haircuts but feel free to share your other tipping thoughts too.