What's more robust and longer-lasting than SD and USB sockets? Flash storage is inherently unreliable and prone to failure, so keeping it on pluggable media is the sensible thing to do.
Well I thought eMMC, but as you indicated that's basically just a SD card soldiered to the board (which I didn't know). So NVMe?
I didn't think this was a really contentious idea. I've had several Pi projects that I needed to mess with because the SD card died. So it seems like a logical evolution would be for the Pi to have more robust storage out of the box.
I think most people with those requirements treat the SD card as a bootloader and keep the main system on a USB connected SSD (or make the system not write-heavy while still only using the SD). It'd be nice to have a rpi that supported NVMe (or just more reliable boot from USB) but I can see why that is not exactly in-scope.
IIRC the most destructive thing to a rpi that is SD-storage only is excessive logging. If you use journald (part of systemd) you can configure it to only keep a small rotating in-memory log, if you use traditional textual logs you can probably do something similar by mounting a in memory fs on the log path.
If you need to keep logs for longer (or between boots/crashes) it's probably good to not use the SD-storage for that. IIRC Tesla had problems with their eMMC storage because they used it for log storage and I've worked on related parts for IoT devices that used SD-cards.
I'm not sure how user-friendly/defaulted all of this is on the recommended rpi distros.
This is how I run mine - SD for boot, USB SSD for root.
You can run NVMe on a Pi4, sort of... if you replace the USB3 controller with a bridge PCB that routes PCIe out the USB ports properly for some other adapters. I don't recall if they got it working reliably or not. And then if you use the CM4, you can certainly have reliable NVMe.
But I'm just not sure it really matters. USB3 SSDs, UAS or not (I've run into UAS issues and while you can tell the difference in a benchmark between having it and not, I can't tell the difference in end use) are more than fast enough for daily use.
The only real change is that the kernel now has zswap provided as a module, so you don't need to build a kernel unless you just think building a kernel on a Pi is cool (which it indeed is).
It's not fast, but it's more than adequate for light desktop use. If you want more guts behind it, the ODroid N2+ is about twice as fast, for not an awful lot more money.
