That average will be brought by junior stylists, but someone who goes to college shouldn't start as a junior (or only for a very short time). Juniors are usually the ones who start at 16 with no training at all. They're not allowed to do anything more complicated than making coffee for the customers and washing hair, and are paid accordingly.

Also not all stylists work full time because it's a relatively well-paid job. One of the colleagues at the salon I was talking about has worked a 3 day week for years, and another works 2 days a week (but she does have another job).

On your other point about older hairstylists, it's a very physical job where you stand in an awkward pose for long hours. Many retire (or semi-retire into salon ownership and doing occasional special customers) by their 50s.