And most Grouponers are bottom-feeders. Just looking for a deal. They're also the most likely to be vocal on Yelp (there was a study somewhere showing how Grouponers/Living Social people were more likely to leave bad reviews).
Groupon's salespeople are so high-pressure and portray an overly optimistic view of what a struggling small business should expect.
Speaking from personal interactions from several business owners who have tried daily deals here. Sure, a business needs to calculate it's ROI, but I think Groupon 1) oversells the value of 'getting their name out there' through their deals and 2) doesn't explain how bad their customers are.
But I suspect it's a correct understanding on the part of the employees. When I talked with servers at restaurants, their experience was that the average Groupon customer was demanding, cheap, and a bad tipper. And they were also unlikely to come back, meaning there wasn't a lot of incentive to invest in a relationship.
I think that's just a misunderstanding on the stores part. A groupon is just another form of advertising (which costs money) - but businesses believe that by offering groupons they will come out ahead.
I've personally gone to places I wouldn't have normally because of groupon and usually spent extra.