- every app has their own licensing system
- I have to keep track of emails, license key files, logins and other bullshit manually instead of having it synchronized automatically at application install. Not to mention I have a boatload of shop accounts that have collected my payment and other personal data (e.g. postal address) and whom I have to trust now that they keep their data secure enough to not have it stolen.
- for subscription stuff, I have to update payment details for an awful lot of individual shops instead of having one single place
- refund policies vary wildly, as is tax compliance for foreign companies
I agree that Apple and Google must be reined in - 30% cut are absurd rip-offs, and the fact that stores can censor legal content (e.g. anything marijuana/tobacco/drug related or adult content) is troubling - but the central store model does have advantages.