There are, of course, a variety of reasons for companies to have shops done. I remember one a bunch of years ago that was for a company with a nationwide presence. I was interested in the shops because I had that company's stock in my retirement IRA, and they had not been doing well. A new CEO was brought in about a year before the shops began appearing.
The first several rounds of shops I did were so tight in their requirements that it would be virtually impossible for any retail establishment to get a good score. Over the months, the guidelines for how to answer the same questions became more and more lax, so 'good reports' were more and more easily attained even though nothing in the store environment had changed.
Came time for the annual report and the new CEO cited 'independent research' as having shown huge increases in customer satisfaction. He proceeded to award himself and his colleagues obscenely large bonuses for the 'improvements' they had brought about. I sold the stock very quickly on this 'good news' because I felt I knew how that improved 'independent research' came about. Sure enough, not too long after that the stock tanked because there was no improvement in sales or margins to go along with all that 'customer satisfaction'.
There are also shops that are to protect the image of the franchise. There may or may not be problems with customer service but rather an interest in making certain that locations are doing what they agreed to do to protect the brand image.
There are many and diverse reasons to perform shops.