Apprenticeships in many (most?) fields are sponsored by the professional organization (akin to a guild) and paid for by laborers at lower-than-master wages. And yet, here is the AMA itself saying the problem lies with federal government funding. Curious. Seems like a convenient scapegoat.
I think you are significantly underestimating how much a medical residency costs.
Also, most apprentices end up working for/with the company/professional that trained them. I'm not sure there are many doctors who employ "apprentice/junior" doctors to work along side them the way a plumber/bricklayer/blacksmith/electrician would.
