I bought an electric car recently and only put up with the minimal haggle of an MSRP cash deal because I was on a sabbatical and had more time than usual. But my partner and I were ready to go for Carvana before my sabbatical or if we couldn't find a dealer willing to stay low-bullshit with us. I ended up calling 6 dealerships and asking my partner to clear her evening just for the one dealership that offered us a low-bullshit deal.
There is a bit of a paperwork dance--also insurance--but, as you say, that's hard to eliminate totally.
Because I want to save money? It literally took about 5 minutes to ask them to add the ~$1500 price of some factory-installed options to my trade-in price and they had a deal.
It wasn't completely frictionless but far and away the main hassle was just car availability. Had I been willing to take a similar vehicle they had on the lot it would have been quicker.
The pain is that people get pulled into negotiations that mix in a bunch of different things (purchase price, trade-in, financing, add-ons) and it's all a bit more than they can comfortably afford.