The Truth
This myth contains a kernel of truth wrapped in a larger falsehood. If detergent residue is left in the carpet after cleaning, it will re-soil faster — because that sticky residue acts like a magnet for dirt carried in on foot traffic. That's exactly what happens when carpet is cleaned improperly by an operator who skips the rinse cycle.
But when carpet is cleaned correctly — using proper pre-conditioning, hot water extraction, a rinsing agent, and powerful truck-mounted suction — all detergent residues are neutralized and extracted. What's left behind is clean fiber, not a sticky film. A properly cleaned carpet does not re-soil any faster than before.
You've likely seen the residue effect firsthand. Spray a store-bought spotter on a stain, get the spot to disappear — then notice a dark ring in the same spot a few weeks later. That's exactly the detergent residue cycle at work.