Hair Cuts at Great Clips (or where ever) do you tip?

I don't understand this tippin concept. Well with wiat staff I do cause they don't make minimum wage. That's different. But a barber's job is cuttin hair. Just like my job when I was workin was a line mechanic. I rarely got tipped, although it did happen on occasion. I say they oughtta just do their job and not expect it. My wife works in the auto lein department for our local huge conglomeration hospital. she doesn't get tips from any of the attorney's offices she files leins for and gets millions of dollars each year for. We do have a local barber shop I used to go to before things got so tight. 15 bucks a head. that's what's on the sign and that's what I always paid until my wife started cuttin it.