Nothing really is done with this data, ultimately. It gets fed to 'analysts' who make models, and if those models don't agree with the decisions the executives are already making, it just gets ignored.
But for other people it may be more revealing, of medical conditions, life changes, etc, especially when combined with other datasets. You moved from a one bedroom to a studio, started buying half as much milk and twice as many frozen pizzas, and take cars to restaurants less? Sorry about the breakup, here are some dating app ads.
Honestly, if my data stayed with the store, just between them and me, I wouldn't be nearly as concerned. The problem is less the data collection and more the databases.