Its more than coupons. These apps track your location, usage and so on then sell this data to a 3rd party. Coupons don’t do that. Do you read full useragreement you accept when installing apps? Most people wouldn’t understand the legalese in those.
A coupon could still be an image you find online that can be scanned and that’s it. Apps are totally not necessary unless they squeeze something out of the user.