I don't understand why a basic understanding of CPU architectures isn't a CS fundamental everywhere.

Even if you have no interest in emulating a CPU or an OS, you really do need to know what registers are, how caches work, what interrupts do, and how basic IO happens.

At the very least it's a practical demonstration of one particular kind of VM, and - if you want to - you can generalise from that to VMs of your own design.

For web apps, not understanding these things can get expensive. Cycles, even cloud cycles, aren't free, and if you take zero interest in optimisation and efficiency you're literally throwing money away.