How Much Profit Do You Want To Make?
Run these generalized numbers:
Cheap Walmart plastic bagless vac for around $100 new. If it lasts for 1 year, you've spent a total of $100 per year or $8 per month. No bags, belts, brushrolls, bulbs or specialized maintenance required. Simply empty the bin and wash/dry the filters. It will probably last for more than one year.
Expensive bagged machine, say $500. Now add belts, bags, other filters, bushrolls and/or brush strips, plus any other specialized periodic maintenance required. In the first year, you may see a total expenditure of $700, which would translate to $58 per month. This amount would drop significantly over time of course. This type of vacuum should last several years though, until the motor (or carbon brushes) wear out.
While a high airflow Sanitaire would certainly clean pile carpets better, under heavy use, say a new bag every other job and new belt every two weeks, costs begin to add up quickly in the professional world.
Since most customers only care about the surface of the carpets appearing clean, why bother with the added expense and time of using high airflow deep pile cleaners? It's up to you, but since everyone is in such a hurry to finish and get to the next job, the added expense and effort on your part will probably go un-noticed.
I own and have formally tested Kirby, Sanitaire, Royal, Rainbow, Dyson and various other bagged and bagless machines. On pile carpets, the high nozzle CFM direct air machines (including 50 year old Hoovers) win along with a few unusual clean air ones.