This is actually a continued subject of debate/study among economists, but the leading theory right now is that it is driven by a taste for variety. In essence, a country may only be able to support three or four major car manufacturers, but there are millions of people in that country that all like different kinds of cars. The best way to continue to capitalize on economies of scale and still deliver on the widest variety of cars for your consumers is to trade between countries/manufacturers.
Pareto_Salad t1_ixtghi2 wrote
Reply to ELI5: Why do countries import and export the same exact resource? by Premium_Woman
This is actually a continued subject of debate/study among economists, but the leading theory right now is that it is driven by a taste for variety. In essence, a country may only be able to support three or four major car manufacturers, but there are millions of people in that country that all like different kinds of cars. The best way to continue to capitalize on economies of scale and still deliver on the widest variety of cars for your consumers is to trade between countries/manufacturers.