In the case of Tesla they have showrooms. They give you a chance to see the car before you buy it and ask questions. The people who work there are not on commission. You can still test drive the car. When you're ready to actually buy the car you go on to their web site and order exactly what you want and they build to order. There's no incentive for the people working in the showroom to push features you don't want.
There is no added value by dealerships. My experience with them is they try and push you to buy a bunch of unnecessary crap.
My father bought a Fisker Karma. The dealership offered no protection from when the manufacturer went bankrupt. The warranty was suddenly null and void. Many Fisker dealerships just disappeared, leaving owners to completely fend for themselves for service and parts. For those that continued to support their customers, any pre-paid maintenance and warranty work now was out of pocket for the owner.
I own a Tesla model S. I have zero complaints about their service. It is better than anything I have seen from any dealership. They don't try and push any unneeded service. They include a loaner car and if a Tesla model S isn't available you can get a BMW, Mercedes or other luxury loaner car, all completely covered by Tesla. In fact, for the warranty they don't require that you have the yearly 12K service done.
When I got my car back from the yearly service, it was washed and vacuumed. They did not have any loaner cars available. I opted to just have them drop me off at work since it was just a few miles away. When they were finished they delivered my car right in front of where I work. My car is a fairly early VIN number.
Tesla also supports independent shops for a number of things. For example, if you need a tire fixed, they won't do it. You go to any tire shop to have that work done. Same thing for body work, though in this case you really want to go to a body shop that has been certified to have the appropriate training, especially since dealing with an aluminum body is different than sheet metal.
For general maintenance you really don't want to go to an independent mechanic for most stuff since they won't be trained. There are a lot of differences between a Tesla and a normal car. The drive train has nothing in common with other cars. Even if Tesla doesn't have a service center nearby, for $100 they will come to you, no matter where you are. If your car failed, they will usually even wave the $100 fee. Many things they can diagnose remotely over 3G or WI-FI so they know exactly what they need to do before they arrive.
For example, my car was one of the earlier VINs that received a defective 12V battery. Tesla contacted me about having it replaced before it failed from their remote monitoring They push out software updates and fixes over the air.
All of the problems I have had with my car were rattles and other issues that have all been addressed in manufacturing for newer cars, yet they will proactively go and upgrade my car to fix these problems or won't ask any questions and just make the changes if I bring it in. My car has a VIN in the low 5000s. Many of these issues require a lot of real-world experience to discover so I give them some leeway there. They have always come through and fixed every issue, no matter how minor it is. Also, they don't wait for mid-year or the next year to update their assembly line. They address the problems immediately. A common problem with the early cars was that the panoramic roof would creek during hot weather. They discovered a shim is required and immediately made the ECO change for manufacturing and went back and fixed all of the cars that experienced the problem. Even if customers don't experience the problem, when the car is brought in for service they proactively fix issues discovered in the early VINs.
No dealership that I'm aware of even comes close to this level of service. Dealerships are leaches left over from a bygone era. There is no reason why one shouldn't be able to just hop on a web site and select exactly how they want their car to be configured and have it made to order.
Also, unlike dealerships, there is no inventory of cars. Every car shipped has a buyer. Right now GM has a huge problem with their Cadillac ELR. They have completely flooded the pipeline such that at the current rate it will take two years for dealers to ship the current inventory of cars. That means a lot of money is wasted keeping these cars on the lot, plus all of the depreciation involved.