In addition to merchants, the group which really ends up losing are customers paying with cash/debit, as they don't harvest any CC rewards from their groceries

In addition to merchants, the group which really ends up losing are customers paying with cash/debit, as they don't harvest any CC rewards from their groceries but still pay the inflated price that merchants have to charge to keep up with swipe fees. I'd argue these high fees are a "tax" on those with poor creditworthiness/financial knowhow