Nesters is an organic higher price type shop, typically in richer middle class areas. Save-on is middle class. BuyLow and PriceMart are generally aimed at lower income /cheap deals.
You also overlook data brokers / AI companies / politicians in your list. Like, even if those had all been poor-person oriented chains, getting info about who shops there and potentially what they tend to buy, would likely be helpful for something like.... say.... ICE in the USA. Heck, you could cross reference that data with the list of names on the voter registry/govt lists, have it filter for 'foreign sounding names', to get a list of targets to follow up on. Poor refugees/immigrants might not be updating their address actively with the govt, but for a grocery discount with a store that supposedly won't release the data to the govt because of privacy legislation.... if a rogue AI 'accidentally' gets it, and a data broker then sells it back to the govt, you've basically laundered that data past the privacy leg.