That would restrict C to memory models with a linear address space. That is usually the case nowadays for C implementations, but maybe we don’t want to set that in stone, because it would be virtually impossible to revert such a guarantee.

There’s also cases like memory address ranges that map to non-memory hardware (i.e. that don’t behave like “dumb” memory), and how would you have the C standard define behavior for those?

Lastly, CPU caches require some sort of abstract model as soon as you have multi-threading.