A huge component of compulsory (either by statute or de-facto as a result of adjacent statute, like mandatory insurance + requirements thereof) professional licensure is that if you follow the rules set by (some entity deputized by) government the government will in return never leave you holding the bag. The government gains partial control and the people under it's control get partial protection.

"oh I'm sorry your hospital burned down mr plantiff but the electrician was following his professional rules so his liability is capped at <small number> you'll just have to eat this one"

I would wager that a solid half if not more of the economy exists under some sort of arrangement like that.