Next time you check out at a Big Box store, look at your receipt ... tell us about your experience and be entered to win $500! They do the same at fast food.... fill out a survey and get a free sandwich. How is this different?
For starters because big box stores dont agree not to do such practices as a requirement for operating. On Amazon incentivized reviews is against the TOS for many good reasons. It is exceedingly frustrating as a seller on Amazon to see competitors violating the ToS to pump their products and make them appear better than they may be.
Even ignoring the whole tos thing though ot is fundamentally different in that a review of the big box store is used by the store to improve themselves ..... An online independent review of a product is used to influence purchasing decisions. Not even in the same ballpark of similarity.