I so wish we could get rid of tipping in the US - or at least as a standard expectation; obviously tipping for a truly above-and-beyond extraordinary experience is understandable.
There is a difference between restaurant wait staff and hairdressers - there's an exemption in the minimum wage law in most (all?) states that allows wait people to earn a base salary lower than the minimum wage, with the difference being made up in tips. Hairdressers aren't subject to that exemption and I'm pretty sure they make a much better base salary than the waitress at a typical chain place. That's one of the reasons I am OK with tipping 20% for meals but rarely do that for any other service.