To be fair, dereferencing a null pointer is also UD in general rather than a guaranteed abort. (Some platforms may provide stronger guarantees, of course; many prevent pages from being mapped at 0x0 as a security mitigation.)

It's worse than this, as even on platforms where actually reading from 0x0 is a guaranteed abort, dereferencing a NULL pointer in C is still UB, meaning the compiler can assume it won't happen and optimize the program accordingly.

To take a rather convoluted example, if you dereference the pointer and then call a function that does a NULL check then writes to the pointer at some offset, it's possible that the compiler will in-line the function, then ellide the NULL check (since you've dereferenced it, the compiler assumes it's not NULL), then remove your dereference if it didn't have side-effects, so now the write goes through without any check. Granted, it would have to be a write to a massive offset to actually hit an allocated page, but I'm sure there are similar scenarios that are more realistic.