Many companies mystery shop, email surveys AND do receipt surveys. Grocery chains, home improvement stores, tire shops, ice cream shops, retail clothing chains, hair cutting place, pet store, electronics, restaurants - off the top of my head. Some surveys offer sweepstakes entries, others offer dollars off next visit.
These companies, in my opinion, are seeking feedback from all sources, hoping to gain insight. I'm sure they realize the feedback from random surveys is not necessarily objective or 'trained'. When I know they're both shopped and opinion solicited, it's a bonanza for the mystery shopper.