O/P cleaning has been an advancement in carpet cleaning, having evolved from rotary cleaning, which evolved from scrubbing rugs on knees or immersing in rivers.
The latest machines have higher speed reciprocation and products developed specifically for O/P'ing which clean vey effectively indeed and with less energy consumption or water usage.
Soil is removed - as we all know - by taking out 80% through vacuuming. The remaining soil is what's attached to carpet fibres and is either removed by pads or encapsulated in a non sticky, crystallised solution and removed by dry vacuuming.
Owners of truck mounted machines in the US and Canada have looked closely at the results and apparently many are going over to O/P cleaning as their first choice.
Why would you, or your customers want tens of gallons of water blasted into their carpets at high pressure with the obvious potential for damage from trailing hoses, leaking or rubbing against valuable items and requiring doors to be open with security risks, when the same result can be achieved quietly and with minimum disruption.