I'm sure many of these occupational licenses have nothing to do with protecting people and everything to do with lining the pockets either of the lawmakers, or indirectly through their contributors and friends.
"Hey Lonnie. I got me a barber teaching school and need more students. Could you put together a law that requires more people to go to barber school? I'd sure appreciate it. And hey, I see you're up for re-election next year. I'll bet I could help out somehow with the campaign."
It's not necessarily about controlling people in this case (although I'm sure that's seen as a nice side benefit by those in power), but rather about $$$.
Yes, I am sure that your scenario happens more often than not, those that don't have direct access to the law makers us the group known as "lobbyists", which also requires registering and paying a fee to the state, although I don't believe they call that particular registration an occupational license, but in all reality it is the same thing.