Asahi started to be developed a couple of months after the first of what would turn out to be the very popular M-chip Macbooks was launched. Those Macbooks are still in people's hands in very large numbers.
Compare that to the number of 1st gen iPads or older iPhones and the demand might not be to the same level to justify the endless reverse engineering effort.
The solution is for the companies to have to open up the device once it's officially not supported.
Or, legally require vendors of general compute devices to provide a common SW-layer with respective documentation, to allow utilization of underlying hardware (not explicitly within the shipped OS, it can also be a separate maintained platform disconnecting the device from the shipped ecosystem).
This would prevent e-waste and put this old hardware to better use. A community OS could then be built on top of this common SW-layer and be maintained for a wider range of devices.
I would e.g. LOVE a "Browser on everything" OS which just provides a Browser OS for outdated hardware, but the only way this could work on scale would be if the device-vendor would be mandated to provide and document the lower layer...
Someone would have to make the economic case for such a regulation as well, i.e. demonstrate the benefit for society and reduction of e-waste if such a law is in place. But the chances for this are razor-thin, especially in today's public/political climate.
The key difference here is iOS becomes a complete brick once the device no longer is supported in the store. We had a gen 1 and 2 iPad and both were just used for Kindle and web surfing but once they pulled safari and apple store they were paperweights.
You need to be on the most recent available minor update.
If the App Store still doesn't work, you can always jailbreak and install apps on your own
Older iPhones/iPads don't have the same longevity as a MacBook, but an iPhone/Ipad sold today could, hardware wise.