Why isn’t landscape orientation supported on many iPad apps?

I have a 12.9” iPad Pro I use as a PC replacement. 99% of the time it’s locked in landscape orientation, connected to my bluetooth keyboard.

I understand there’s quite a few apps that don’t have a separate iPad interface, and they show up as an iPhone-sized display, with the option to stretch to fit the bigger screen, but only in portrait orientation. For these apps, why isn’t there a way to show that small display in landscape mode? Is this something that will be added in the future? Right next to the icon that stretches the iPhone app, there should be a rotate option to stretch in landscape mode. DoorDash, Postmates, Credit Karma, Instagram, Tik Tok, are all examples of the behavior I’m describing, so I just don’t use them at all on the iPad.

Basically to use my bluetooth keyboard (Logitech) on these apps, I have to type/view at a 90” angle from the app, or use the desktop safari site instead of the app if there is one. It seems like a major oversight to me and I’m looking for clarification on if I should expect this to continue or if it’s in the works, where I can submit this feedback, etc.

Thank you!