Why do we need 3rd party stores? Why not just have a standard for an app endpoint url that iOS knows how to interact with. So I could publish an app on a private domain and then iOS would know how to download the app and check for updates from that end point? While there is value in a centralized store to search for apps (and that can certainly stick around), I don't understand why apps are forced to be hosted centrally in a store, Apple or third party.

Ex: To install the "Pepsi" app just go to pepsi.com and click the install app button. Then iOS could take over from there.