Post war is, in my opinion, when modern car manufacturing really took off.
Before that there is a lot of horrible stuff to deal with like building chassis for bespoke coachbuilders to put bodies on, weird chain drive cars, band brakes, bodies that are so blocky and coach like that our car design system won’t really work at all. I also think that the 1900 - 1940 part of other games like Detroit was usually the weakest and least fun part, as tech was advancing slowly, all your cars were horrible and the market for cars was pretty small anyhow, I’d rather not put effort into that and instead spend that time making the rest of the game better 