Someone once told me that the main reason they needed service reports was to gauge the level of interest in different areas and so they'd know how much literature to print. Really, they could do the same thing if people submitted anonymous reports. They also could simply use the stats from the amount of literature the congregations order each month. I think the main purpose behind reporting is to exercise control over congregation members, and to intimidate them. They want to know who is "weak". I'm sure many lie on their service reports just to keep elders off their backs. I did, for a while. Once I stopped going out the elders were bugging me to turn in reports, so I just started giving them reports with all zeros written on them.
In my last hall there were 14 regular pioneers?, yet over 30% of the territories were untouched in over 2 years. I'm sure they were not knocking on doors all that time, but I know the local Tim Hortons does a great business from the JW's here.