Suppose for a moment that you are building a new processor for mobile devices.
The mobile device makers - Apple, Google, and Microsoft -- all have "App Stores". Side loading is possible to varying degrees, but in no case is it supported or a targeted business scenario.
These big 3 all provide their own SDKs. They specify the compilers, the libraries, etc.
Many of the posts in this thread talk about how critical it will be for the compilers to produce code well suited for this processor...
Arguably, due to the app development toolchain and software delivery monoculture attached to each of the mobile platforms, it is probably easier than ever to improve compilers and transparently update the apps being held in app-store catalogs to improve their performance for specific mobile processors.
It's not the wild west any more; with tighter constraints around the target environment, more specific optimizations become plausible.