What licensing can do is provide an incentive for general practitioners of a particular craft to follow a certain set of standards and guidelines for basic safety. If licensing is required for access to certain materials and maintaining your license requires either passing some sort of "don't be an idiot" safety course (or having your "lab" available for inspection) then this low bar can keep some of the idiots out of the way and can be used as a stick with which to beat upon well-meaning people who engage in gross incompetence regarding safety.

What licensing can do is block competition to the established powers. Do you think it was from the goodness of their hearts that Microsoft was pushing the attempt to license "software engineers" and programmers a decade ago.