I haven’t found a good, well-referenced article on this topic, but the short version seems to be lobbying of state governments by car dealers back in the 1930s,

I haven’t found a good, well-referenced article on this topic, but the short version seems to be lobbying of state governments by car dealers back in the 1930s, and continued lobbying since. Incumbent car manufacturers had no particular incentive to upset the applecart, but Tesla had the opportunity to see how insane it was. Interestingly, BYD has chosen a direct to consumer model here in Australia (if you haven’t heard of them, you soon will). Mercedes has now switched to an agency pricing model where the dealers sell on commission and don’t own the cars, so Mercedes can legally control the retail price.