It might be like that, or it might not. Maybe the car manufacturers take a public view that's different from their private view. Why would a state demand extra hurdles that cost its residents more money? Could it have anything to do with creating barriers to entry for other manufacturers to sell their cars in that state, basically making it difficult to buy a car that isn't part of an established brand?
I think manufacturers actually vary their opinions sometimes. If they are new without many resources, they might prefer to sell direct to customer. If they are mature, it could be looked at two ways. On one hand there is a lot of work to do in order to sell and support the vehicles that can't be done in a centralized fashion. They can afford to do the work themselves by setting up a bunch of dealerships all over the country. But it is questionable whether the manufacturer can actually do it cheaper than the individual dealers. As for this:
>Research shows that as a result of these laws, retail prices for cars are higher than they otherwise would be.
There are three points I have for you to consider. For one, is it possible for people to get service from dealerships that provides value that is hard to appreciate? For example, they can fix issues quickly without shipping the car off, develop relationships with customers to help them fill their needs, do trade-ins (how would that work when dealing with a manufacturer directly?), or any number of other things that we know they do for customers. Secondly, how is this research conducted if car dealerships are mandated by law? Finally, if the manufacturer takes on the dealership role, it has to bear basically the same costs as the independent dealer. So where is the actual savings going to come from? Do you think you can negotiate with a factory outlet to get a better price?
Here's another thing you might want to consider. I know it's going to sound crazy, but in some cases people are served better by allowing prices to fluctuate. How? Well, the people more willing to buy a particular car (with a supply constraint) are willing to pay more, and that is only feasible if the seller has scope to negotiate. If there is no scope to change prices then the cars just go out with equal priority, possibly depriving someone of their dream car while someone else who appreciates it less is the one who got it first. The individual sellers on the other hand have varying supplies of cars from the manufacturer. There are similar benefits to the individual dealers in having that flexibility, although that doesn't matter in the question of whether or not independent dealers should exist.