Extraction pre-sprays and detergents used correctly do not promote resoiling. But just look at the list of TLC's, pre-sprays, detergent and acid rinses available from the industry's leaders, and you'll see that there are an enourmous range of variables to allow things to go wrong. Good training and experience will virtually eliminate this risk of resoiling.
Modern detergents usually leave a dry crystaline residue. Very small quantities which should not promote resoiling whilst dry. However, detergents are water loving and can absorb moisture. If this happens, the residue can then become sticky and do what it's designed to do ie attract soil. To be honest, from straight forward correctly executed cleans, this is not a problem. Most problems tend to come from dirty traffic before the carpet had dried. Remember, a typical wool yarn will absorb upto 30% of it's own weight in water and still feel dry, and in humid conditions this will apply BEFORE you've cleaned it. A good rule of thumb, regardless of the equipment used, will not return to it's driest possible state until about 48 hours after cleaning, even though it felt dry within a few short hours.
The free rinsing detergent pre-sprays such as Spitfire Advanced and CitraFresh along with Micro-Spliitters are all rinsed with just tap water, so there are virtually no resoiling problems associated with these types of products, again if used correctly. My own experiences of using regular type detergents was that, because of the way I work, almost all of my HWE was done with Fibre and Fabric Rinse. Resoiling, for me, was usually down to traffic before dry or from other cleaners.
Safe and happy cleaning
Ken