Why do these apps have to come from an Apple or Amazon web store? Can’t any of these web sites just offer to download their own app directly from their web site? Why does there need to be some third party distributor involved?
No, they can’t. The Apple app stores have Apple as a gatekeeper who has control of what apps get into the store and Apple gets a 30% cut of the app sales. Unless you jail-break the OS, no luck side-loading the app.
dvwjr