The same thing is true of many high paying white collar jobs. Lawyers, physicians, CPAs, PEs all have to pass exams to become licensed. Many of these are gated by non-optional schooling. E.g., in most jurisdictions, you cannot just pass the bar and become an attorney. Others, like physics and architects, are additionally gated by mandatory apprenticeships.

Gatekeeping is not some thing that just the scare quotes skilled trades do.