I'm staggered that anyone admits to not vacuuming, I've been convinced since early IICRC courses (prior to that I didn't vacuum). I find the clean to be easier, quicker and the results better with a pre vac than without. Mind you I will also use a cotton bonnet to work in the prespray* then extact with a truckmount and even sometimes bonnet finish with a clean pad. Some of the worst cleans I've ever had to do have been when a carpet has been wet cleaned with a low power portable, no pre vac and all the S**t has been washed right down to the base of the fibres.
* another waste of time in the eyes of some "professional cleaners"
Chris Meyer NCCA 1053