The best argument I've hard in favor of dealers is that they introduce competition in sales of a single brand of vehicle. Instead of Ford having a monopoly on Ford vehicles and selling for MSRP only, you can shop around Ford dealerships that all sell the same product but have to compete with eachother on price or whatever.

That system starts to break down when, like in recent years, dealerships collectively decide to stop selling vehicles for MSRP or below and all tack on thousands of bullshit dealership markup fees. Also dealerships are exclusively run by scum of the Earth which massively taints the entire car shopping experience.