These Shoppers are not just random people who take up an assignment and give feedback. Okay, most of these Shopper are not like that. These Shoppers take the task seriously.
The term shopper also has a wider meaning. Because they are in actual fact, part of your customer base. The demographic of consumers that a company is trying to reach.
Companies can then ask questions on their own. For example, is it fair to penalize a staff due to poor service during a busy period? Is it alright for the basics of customer service to not be met, just because it was busy?
Most importantly, we find out how the shopper feels about these situations. To a Shopper bad service is bad service. Would some shoppers be understanding?