even if they are 100% cloth in their...i dont see how they would scratch anything. Or are you talking about car washes that dont use 100% cloth
Because it could pick up loose debris (little rocks, pieces of glass, etc.) from your car or other cars, and essentially wash your car with it.
The fact that it's cloth means that it can pick loose dirt and shit up fairly easily. Who's to say that it doesn't stick to the cloth, and then drag it across your car.
Hell, some people won't even use power based soap to wash their car because they think that one little undisolved pellet can scratch their paint.