Every sales graph I've ever seen has relatively cheap cars such as the Fiesta, Golf, Corsa, etc. at the top. Not big Mercedes or BMWs.
But people who want saloons and estate cars are largely buying from the three Germans, and not Japanese or Korean.
So in the USA, or at least in California they are very common. Part of their popularity is their fleet use makes them direct cheap in the used market, and they tend to be pretty reliable despite the complexity of two separate drive trains.
Personally I drive a cheap car. Average new car prices have gotten crazy high relative to median incomes, enabled by low interest long term financing. A lot of buyers are ending up overextended.
Following your logic the model 3 isn’t a luxury car either.
[1]https://www.caranddriver.com/features/g15379432/small-entry-...
https://www.autocar.co.uk/car-news/best-cars/top-10-best-lux...
Edit: Sort of reminds me of the differences in defining "class" between the US and the UK :-)