It's illegal to wash on the driveway or street over here. Well, technically not, it's just illegal to wash it in a way without proper waste water disposal, which means that you could put up a water barrier (think kiddie pool) to collect everything and then dispose of it properly.
Rain water drains usually don't go to waste water treatment, shit might get in there from ordinary use but there's no need to put all kinds of random detergents and polishing agents and whatnot on top of that. Also at least on the Autobahn they have separate rain water channels to catch all the tyre microplastics etc. And if you can afford a car that's worth washing you can afford going to a DIY washing place stop whining.