A 3,000-pound washer is great for a lot of things - buildings, decks, roofs, trucks, - I've used them a lot, and in fact when I got tired of renting them I built my own using parts from Grainger
but...
They create huge amounts of spray, which carries whatever kind of crud you are cleaning. If used indoors, this fine spray will coat every surface in the room you're "cleaning", if not most of the rest of the house or restaurant. Apart from the problem of routing out tile grout or stripping paint.
These are strictly outdoor tools.
Mike