It does, but not as radically or frequently as software. The tools stay (mostly) the same. A reasonably experienced barber should be able to learn this year's haircut fashion after a couple customers.
He said barber, not hairdresser. Men’s hairstyles really don’t change that fast and the degree of technical sophistication involved doesn’t change radically over a career. You can get better at being a barber but there’s always going to be demand for a short back and sides or a buzz cut.
I don't think human hair has changed that much over the past 200,000 years.
You don't? Black women are constantly complaining about how their hair takes specialty tools and special knowledge only possessed by barbers who specifically learn to care for black hair.