When I began cleaning in 1956, a rotary shampooer was the ONLY way to clean a carpet.
And it had been around for a very long time before I began.
But just like most anything, someone who does not know what they are doing CAN cause damage to any carpet- or anything else for that matter.
I am sure that is the reason the carpet mill says something like- "If you cause damage they will not cover the damage."
Not because a roto will actually damage a carpet.
Knowing what you are doing and how to do it is the key.
Gary