Multiple reasons.....
1. Individual owners / franchises paying for this work.
2. The end-client only wants a specific regions, selection location, etc. shopped, whether it be high-traffic, locations in urban settings, etc. Why pay for locations that have no quality control issues? It's a waste of money on the client's end to pay for EVERYTHING, the Cadillac and reducing their ROI, vs. focusing on problem areas only and optimizing their ROI.
Shopping the Greater Denver Area, Colorado Springs and in-between in Colorado. 33 year old male and willing to travel!