Barbers tended to use what they learned on. Once hollow ground became popular few wanted the old wedges and such. They were backward and hard to maintain. Schools did the modern thing. It was mainly the old timers who learned with wedges and part wedges who continued to use them. Also don't forget barbers were in a hurry and wanted to do as many clients as possible to make more money and the hollow grinds were smaller, lighter and more maneuverable which translates to faster.

As far as the barbers use thing I would imagine it was a marketing ploy though originally they might have been marketed for professional use and that changed over time.