[wyldfire]

One (modest) force that coerces the market: you nearly always must attend law school. Unlike Lincoln, John Adams, Marshall, et al, you have to get a degree from a law school in order to become an attorney. Apprenticeship is peanuts compared to getting a degree (provided you can find a sponsor). There's a handful of US states that still permit apprenticeship, but most do not.

[amelius]

Ok, then why is law school so expensive? It seems to me that classes could be offered online without practical problems, and exams could be organized on a national level.