> Just look at any popular app on a tablet - they all have massive borders/sidebars and within those it's just the phone app as-is.
What apps are you using? That's not the case for any of the iPad apps I use anymore, though early on it was fairly common since quick ports could be made by checking the "release for iPad" box or however it worked back then. That was 15 years ago, though, things have changed quite a bit since then.
There is a difference between iPad and iPhone apps. The former run full screen, and the latter letterboxed.
I don’t use iPhone apps on this iPad Mini, they are too painful. I use the Instagram and Blue Sky web sites instead.
I don't use either of those services so I was unaware. So I guess there are still some apps out there without a proper iPad interface. I haven't encountered any in at least a decade though and they seem to be in the minority. Apple has gone to great lengths to make it easy to at least make something that fits on the iPad even if you don't try to make it properly native and use the screen real estate effectively. So that strikes me as laziness on the part of the Instagram and Bluesky app developers to not even try.
One could make the case that nobody needs tablet apps because web apps work well on tablets -- without annoying notifications or annoying popups to access privacy violating features [1], without adding clutter to an already too cluttered "desktop" of icons that all look the same, etc.
[1] that nobody in their right mind would click on, but I guess somebody with dementia might...
I don't totally disagree, though I dislike most web apps because, well, they require an internet connection too often (if not always). And I don't trust their creators to be any better at not violating privacy (my data is typically stored on their servers, after all).
With that said, I'm not sure what you're replying to in my comment.
Android has unfortunately trended the opposite direction - apps that once had tablet UIs dropped them in favour of big phone UIs as they did redesigns around 2016-2020. I dropped out of the Android tablet world in 2019 for a Windows tablet, and most recently went for an iPad this year, so maybe Android has recovered ground there, but judging by how few Android tablets are actually on the market, I wouldn't be hopeful.