I guess it has to do with the fact that everything is greyscale nowadays ... did you notice there are no more coloured cars, and the few that are there are all faded.
I'm guessing limited car colors benefits the manufacturers more so than the customer. Less choice means less cost. Additionally, by avoiding 'polarizing' colors, they likely won't have issues with unsellable stock.
I think because people are visually overstimulated from all the content in their phones, they prefer plain minimal design in the physical world.
Podcast: https://freakonomics.com/podcast/car-colors/