IMO, there's a couple things going on there. First, grocery stores work on a 3% margin, so if they have a ton of returns on something, it costs them a ton of m

IMO, there's a couple things going on there. First, grocery stores work on a 3% margin, so if they have a ton of returns on something, it costs them a ton of money from credit card fees and wages, and possibly from losing the cost of some portion of the product. Second, grocery stores have limited space and are picky about what they'll put in their store. They want quality goods that will sell well, and they don't want to cannibalize other products that would make them more money. So random supplements don't find their way to their shelves.