I bet your attorney is a member of the state bar. And enjoys the privilege of limited competition by denying to those who did not play the game access to practice law, and in some instances, even represent themselves at law.
Your mechanic, however, completes in a market where there is no barrier to entry other than tools, equipment, facilities, access to vital information (at a price), and knowledge/skills/abilities. Training is not essential, however desirable and helpful it must be.
Your attorney is part of a cartel, however useful and productive that may be. They don't even have to serve you terribly well. Your mechanic will try harder, they have to. And if you think attorneys are somehow practicing a trade more important than all others save doctors, well, maybe. Maybe.