Dealer direct, sounds good. Until you find out that car you really want has a demonstration center that is too far away, in a place you don't want to go. Until you find out repairs are done at an authorized shop that handles so many brands they cannot get it right. Until you have serious problems with your car and that manufacturer is so far away they can ignore you for a good amount of time... and so on.
While not everyone has a good experience at a dealer I have never had a bad one and considering the number of vehicles I have gone through, well. Dealers aren't there just to sell cars. They they maintain them, they work to keep you happy so you come back. This means they act as go between consumer and manufacturer and can often push the manufacturer to fix things they might just overlook.
Tesla is fine as it is now simply because they don't sell enough cars to matter, let alone to the majority of people their cars are not affordable and the customers who do buy have the time to go anywhere they need to to buy a car or even have someone go get it. When, and it is a very big when, Tesla has any real volume let us watch how they handle problems