I do not look at my clothing, plates, bed linens, or CARPET with a microscope. Neither does anyone that I know. They call that “obsessive compulsive” and they have medications to help control it. Suffice it to say, if you use a cleaning method that meets the objectives of your clients and you can get a fair price for it, then you are doing good. I do not want to eat a meal off of my carpet backing. I don’t expect it to be as clean as a dinner plate.
All of us agree that many soils and contaminants pass through the carpet and settle on the pad. These soils and contaminants are still present even after the most thorough cleaning. Should we begin pulling up the carpet and cleaning the backing and pad? I would venture to say that if you are cleaning to “industry accepted standards”, you will remove a great majority of the soils in the average carpet.
Nobody that I know is breathing with their face shoved down into the carpet pile. Nobody is licking the carpet except for infants, but they lick puppies in the mouth, too.
Delight your clients, get paid, move on. Strive for excellence, but do not obsess over perfection.
It does not exist!