This would be un-manageable.
One of the reasons is they're updating/changing fundamental APIs. Take Swift for example, this is still a construction site and it shows if you've developed with it.
If you decide that a function needs another argument or behavior or should return another data type (Double instead of Integer for instance), you can make every app that uses this API crash instantly. Which means that all these apps need minor changes to accomodate the new APIs. This is why even though they can't change a billion things on a two-week release cycle, the updates are rather big (over 1 GB).
Now, if you change an app for an API and then you need to change the exact same app for another API, this is where it becomes un-manageable. Real-time updates are a dream and will never happen.