Flash storage might be the highest-margin component sold by Apple, so there's a conflict of interest with filesystem features that reduce the need for storage.

That seems a little tinfoil hat considering the largest consumer use of storage is photos & video, neither of which compress any more anyway.

And that Apple is heavily pushing the HEIF/HEVC formats in ways that provide similar image quality with lower storage uses.

This is a macOS thread, but it would be helpful if Apple allows micro SD cards to be connected to the lightning port of iOS devices.

Like this[0]?

I have no idea how well it works or what its capabilities are, but it seems to be exactly what you are looking for.

[0] https://www.apple.com/ca/shop/product/MJYT2AM/A/lightning-to...

That is mostly limited to copying photos and videos to/from the "Photo Roll".

There are many thousands of applications which process other file formats. Some of them have natively implemented support for a 3rd-party (expensive) storage device called iXpand, which itself comes with a poorly implemented app. These third-party applications are poorly and pointlessly (re) implementing basic OS file system I/O functions.

Is it possible that these pointless I/O hoops are hampering uptake of $1000 iPad Pros for "laptop" use cases?

Macbook Pros have use cases which extend well beyond photos & video.

lz4 and zstd are cheap in what? CPU cycles? Apple cares more about energy use these days (correlated but not equivalent), maybe it's not a good tradeoff?