> Have you never met a bad doctor? A shoddy lawyer? A barista with a PhD?

I presume the implication is that bad doctors and shoddy lawyers exist and just because they have advanced degrees doesn't make them good at what they do. This seems reasonable.

BUT, I find it fascinating that people who aren't doctors or medical experts think they can spot a "bad" doctor or people who aren't lawyers or experts in law think they can spot a "shoddy" lawyer.

A good doctor/lawyer makes good decisions and executes beneficial actions given the facts surrounding a situation. It's pretty hard to judge whether those decisions and actions are good or bad if one isn't an expert.

That's a huge motivating factor for professional licenses.