Why are wiper motors switched ground?

[davepl]

Does anyone know the historical reason why windshield wiper motors always seem to be switched ground instead of swtiched power like everything else?

I assumed it was for making the "parking" feature on hidden wipers, like on my 69 Pontiac, easier to implement. But in the other wiper wiring thread (didn't want to randomize it) they say that they've been switched ground going all the way back to single speed stuff.

So why not switched power? Being switched ground means they need those fancy isolated rubber mounts and various other complexities...