It doesn't bother me so much when a business does this cause they're a business and of coarse they're going to try things to save themselves money. In my experience working retail surveys just won't ever truly replace MSC's. Customer information especially when an experience is good, is hard to come by and even more difficult to get details. Often times they'll get subjective info like "it was a very pleasant experience" or "the cashier was very nice". That doesn't give the company much to go on, on what the customer thought made their experience pleasant or what the customer thought made the cashier nice.
What DOES make me mad is when an MSC agrees to send out surveys for a business to their mystery shoppers "for a chance to win $500" or something like that. That's INSULTING to me. A certain MSC out there who happens to have the same initials as a derogatory term starting with the word Mother, is famous lately for this.
They're basically saying they think your detailed input isn't worth anything and as an MSC they should not be helping the businesses by offering an avenue for the business to pay less then a true mystery shop but still get detailed results