oh you bet, specially if you go to some outskirts (rural) - you see mud covered pickups going into these washes.
that mud is now part of those brushes and nicely scratch the surface.
btw - its almost useless for me to wash my cars, whenever I wash them - it rains, so I wash them in the rain 
apply shampoo with umbrella in hand - let it rinse itself, fastest car wash in the world.