iPad Landscape Mode on Portrait-Only iPhone Apps

When running a Portrait-Only iPhone app, the iPad should give the option to continue in landscape mode (I say continue because with the introduction of the magic keyboard, many users exclusively use the iPad in landscape mode). I cannot think of a reason to not allow an app to use portrait dimensions in landscape mode, leaving the margins on the sides black. This would be a much better user experience.

Whenever I see answers to this question asked elsewhere, for some reason the app-developers are blamed. This makes no sense to me. Yes, an app-developer could add a landscape mode option, but for many apps, the vast majority of their users are on iPhone where a user almost always starts in portrait mode. The iPhone is a portrait mode device. It often makes no sense for an app-developer to allocate resources to adding a landscape option when less than 1% of users are on an iPad and would make use of it. So if apple wants to fix the user experience of the iPad, it should support portrait-only apps rotated in landscape mode still with portrait dimensions. This to me is the biggest blocker to making the iPad feel like a computer. Usually when using a computer, you don’t have to pick it up off the desk and tilt it sideways to read, then put it back down to type on your keyboard.