Sooner or later after you've had your fun refusing and denying your predecessors, you realize why they do things the way they do, become wiser, and go back and undo and redo all the fuckery you caused with your refusing and denying.
It would be nice if we could get that realization without first having to fuck everything up, y'know?
As the saying goes: "good decisions come from experience, and experience comes from bad decisions". It would be great if we could all come out of the womb with enough education and experience to function as responsible adults in modern society, but we don't. Society (rightfully) allows people some leeway in doing dumb shit so that they can learn firsthand why it's dumb.
It's all cute if this just happens during our childhood years, where most actions hold no real consequence. It's when this extends into the real world with very real consequences that it gets really wasteful.
Licensing and training has a very real cost as well of course, and for many topics the cost of forcing everyone to get a license would outstrip the benefits. So you either have to spend on training, or you have to spend to fix the mistakes of untrained people, or a mix of both. There is no way to bring the waste to zero.