I find it really amazing that people can't seem to grasp the concept that in days or old barbers were highly skilled at giving shaves and people assume that only they can give themselves great shaves or that there must have been plenty of bad barbers. I grew up in NYC and back in the 1950s when I was growing up barbers probably did more shaves than haircuts yet no one says they can give themselves a better haircut than a barber can.
As far as some barbers being bad goes if you went to a shop to get a haircut and the barber did a poor job would you go back to him. The same with shaves. Most shops in those days served a pretty small community even in a big city and a poor shave or haircut meant a reputation at that shop. it would also translate to no customers and the shop or barber would be looking for another line of work.
Unlike the present day when people expect mediocrity in everything and seem surprised when something is done right the first time back then attitudes were different. It was expected that things were done right the first time and there was little toleration for shoddy workmanship or skill.