Well ive been scrubbing for 27 years. I have glides and agitation brushes as well as a Host for agitation, but its my scrubbing action that imo makes all the diference, both to the quality of the clean, the thoroughness of the rinse and the speed of drying. This is what I have found on the majority of carpet in average condition, that I clean. Of course a well maintained lightly soiled carpet may well only require a sweep back rinse, however I have exhaustively trialled techniques with diferent carpet types and degree of soiling, with and without glides, and this is the conclusion I have reached. I do get occasional back trouble, as I have ever since I started in this business, and I find 'Voltarol' gel invaluable!
Dave.