Fair point. Around where I live, they seem pretty scarce the few times I've looked at the app out of curiosity. I don't know how long a typical pickup would take. But there's certainly some density level of drivers/passengers below which the market doesn't work. In fact, any percentage decrease presumably decreases service everywhere to some degree and shrinks the areas where Uber/Lyft can effectively operate at all.

I do use private cars but pretty much to get back and forth to the airport.