The number 1 thing they are paying for by a mile is reach. Not any particular service offering. Your listing the app store can be nearly as important as your SE

The number 1 thing they are paying for by a mile is reach. Not any particular service offering. Your listing the app store can be nearly as important as your SEO ranking of moreso depending on your business. It's why Google can still charge pretty hefty fees despite not locking users in nor doing all that much for app quality. If you're not in the Play Store, users won't find you.