Margins are not usually narrow in the food business. I don't know where "0 to 15%" comes from. But businesses want to increase sales by getting new customers, not by having regulars pay less. Perhaps the businesses are hoping in the long term, they gain new, loyal customers that stick with them even after UberEats or whatever delivery service stops subsidizing and doing promos and becomes cheaper to cut out the middle man like in the olden days.
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