Here in Michigan you need to be certified by the state to work on a street motorcycle for money. Most of the test was ridiculously simple and there was absolutely nothing about tires, brakes, lights or anything remotely related to the safety of a motorcycle. The only slightly challenging part of the test was things a machinist needs to know, like how to read a micrometer.
I outsource all my machine shop work so I don't ever read a mic. Interestingly, the machine shop guy that does read it doesn't need to be certified by the state. .
Easy enough to tell the test/certification is all about the money.