A lot of this is a result of how trade licensing works. In most states it's not about whether you know how to do something -- you can't just take a licensing e

A lot of this is a result of how trade licensing works. In most states it's not about whether you know how to do something -- you can't just take a licensing exam and get a license even if you know the material -- it's about having access to someone who already has a license to sign off on you. From which you get two consequences. First, if you know someone who already has a license but doesn't know what they're doing or isn't a good teacher, they sign off on other people without actually teaching them how to do a good job, and then you get even more people with a license who don't really know how to do the job. And second, because the existing license holder has to sign off on several years worth of hours for someone new to get a license, you deter people who would do a good job but -- because of that -- have more opportunities in other industries where you don't have to spend a large chunk of your adult life beholden to someone else because it's still prohibited by law for you to strike out on your own, in an industry that people would otherwise want to enter because they want to do exactly that. Which both lowers the average quality of the candidate pool and creates shortages by lowering the number of candidates.