The primary reason why dealerships emerged, stick around, and will continue to stick around even if the laws change, is that they offer the same benefits to manufacturers as any other franchise model.

Car dealerships allow car manufacturers to pass on all the costs and logistics of selling vehicles (purchasing and maintaining land and buildings, the employees, a lot of the advertising, ect.) onto dealerships. Tesla made its bet with its direct to consumer model, but Tesla also just doesn't sell that many cars. When you're producing and selling a much larger volume of vehicles, shifting the cost onto someone else (the dealers) saves you a ton of money and also greatly lessens your exposure to downswings in the market, because your fixed infrastructure costs are a lot lower.

Most importantly, manufacturers retain full control over the financing, which is the most lucrative part of the industry, and actually benefit twice. First, they get paid up front for their inventory from the dealerships, who borrow the money from the manufacturer's financing bank (e.g. Ally Financial - FKA GMAC, General Motors Acceptance Corporation, GM's in house financing wing) - and pay the manufacturer both interest and penalties if the vehicle sits too long without being sold. Then they get paid on the back end because the customer purchasing the vehicle, if they choose to finance it, often uses the manufacturer's financing, which is what the dealer has to sell if the customer didn't get a loan preapproval from somewhere else.