It rinses grime off with force instead of you dragging it around with a mitt, which cuts the risk of scratching. It also drives the pre-wash and snow foam stages.
Not at sensible pressure and distance. Keep the nozzle back from the panel, avoid blasting straight at edges and trim, and it is far safer than heavy contact washing.
A domestic unit with enough flow to run a foam cannon covers most needs. Flow rate matters as much as pressure, so check it will feed a cannon before you buy.