NPR’s Planet Money observes licensing in certain industries and why it’s illegal to braid hair unlicensed:
In the 1950s, fewer than 5 percent of American workers needed a license to do their job. Today, about a third of workers need licenses. The increase has been driven partly by the shift away from manufacturing jobs (which don’t tend to be licensed) and toward service jobs (which often require licenses). But it’s also been driven by a push from professions themselves. Licensing rules make it harder for new people to enter a field. That’s good for people who are already in the profession, because it limits competition and allows them to raise prices. So professions go to lawmakers and say: You need to regulate us.