I remember grabbing the 50+ page "magazines", full of cars listed by individuals, on the convenience store racks back in the 90's. And then finding them on craigslist or Ebay, and I guess now it's Facebook marketplace (see very few individuals listing on cars.com, or autotrader.com, or cargurus.com, etc). But even on Facebook marketplace the "individual seller" is often a representative of a small lot dealership. It was seeming to me that it was harder to find cars truly listed by individuals, but it may just be the way I find them make it appear to be fewer than it really is. The last couple years even trade in values were way over what people might have originally paid for their cars, so no incentive to sell private party - to me the main inventive to selling private party was to net more money. It can be a pain in the ass, so it better be 10% more, at least, than what I could get on trade in.
I list a vehicle now and it's constant trade requests, or can I rent to own, or "best I can do is 50% of your asking price".