The aim of professionals who spend their time cleaning carpets is to get the carpets as clean as they can and as dry as possible.
This Wikipedia entry explains how the system works:
Encapsulation In the 1990s, new polymers began literally encapsulating (crystallizing) soil particles into dry residues on contact, in a process now regarded by the industry as a growing, up-and-coming technology; working like “tiny sponges”, the deep-cleaning compound crystals dissolve and absorb dirt prior to its removal from the carpet. Cleaning solution is applied by rotary machine, “CRB” counter rotating brush, brush applicator, or compression sprayer. Dry residue is vacuum able immediately, either separately or from a built-in unit of the cleaning system machine. According to ICS Cleaning Specialist, evidence suggests encapsulation improves carpet appearance, compared to other systems; and it is favourable in terms of high-traffic needs, operator training, equipment expense, and lack of wet residue. Encapsulation carpet cleaning also keeps carpets cleaner for longer periods of time compared to other methods. Encapsulation also avoids the drying time of carpet shampoos, making the carpet immediately available for use. The use of encapsulation to create a crystalline residue that can be immediately vacuumed (as opposed to the dry powder residue of wet-cleaning systems, which generally requires an additional day before vacuuming)is a newer technology that has recently become an accepted method for commercial and residential carpet deep cleaning.