They are pretty common in passenger cars too, google 'standheizung' or 'stationary heater' and you'll find a ton of them. You might not realize that that is what it is. On cars sold in the Nordics and some German brands it is just a checkbox during the order process.

It's quite normal in colder climates, but mostly in Diesel cars. I had it in my VW Multivan. I've never heard of anyone installing Webasto in their EV.

There are all sorts of China knockoffs of them going up and down the size scale.