Or if you want something more performant and reliable than eMMC.

Exactly. There are so many use cases for the RPi that very often people wonder why you’d ever want it to support X. When the people that want feature X have a completely different use case in mind.

Embedded people don’t need faster IO, so why use it? If you want to use it as a desktop, you might not need eMMC, but an M.2 slot would be critical.

It’s really an interesting ecosystem of uses.

Do you know if anyone makes a back-plane/carrier board (not sure on what the actual name is) for hosting/holding multiple CM4? I found a few for the CM3 but they seem a bit cost prohibitive.

There is at least one other multiple-CM4 board 'in development', though I can't share any detail, other than keep an eye on this page for when it might appear: https://pipci.jeffgeerling.com/boards_cm

Not affiliated with the project in any way, but I do know this one is launching soon! https://turingpi.com/

Edit: Spoke too soon, only works with the CM3/3+. Leaving it here in case anyone is interested.

They have a v2, thanks to the user who commented after you! https://turingpi.com/v2/

Does the eMMC get corrupted as easily as the SD cards do?

SD cards don't get corrupted easily, if you buy the right ones. (Unfortunately most people don't, and end up blaming the Pi for being unreliable.)

Well, it's not easy. Brand name doesn't get you anything in this department, you have to track down "industrial" SD cards.

On top of that, it's 50/50 in my experience as to whether the fault was the microSD card, or a weak / insufficient power supply (that's the main reason, I think, the Pi Foundation now makes their own).

> if you buy the right ones

No offense but that's true of everything and incredibly unhelpful. As others have pointed out, you can't rely on name brand or even product line.

This isn't an issue isolated to Pis either, GoPros, among other devices, are notorious for eating microSD cards as well.

Not nearly as much. eMMC is designed for these use cases.