It goes even further than your second point, for many professions: We don't just want to signal other people that doctors, nurses, engineers etc. have been edu

It goes even further than your second point, for many professions: We don't just want to signal other people that doctors, nurses, engineers etc. have been educated. We want to validate that they've actually learned what they need to know in order to not cause uneccessary injuries and death to other people.