Computer memory is already a big array. Probably what you are thinking of is that processing array items sequentially is a lot faster than following pointers, but in the cases I'm talking about, you end up using array indices instead of pointers, which isn't much faster.

Yeah, but now logic bugs can cause memory leaks, doing use-after-frees, etc, without any kind of tooling to prevent it (nothing like valgrind to catch them). Sure, they won't crash the program, but sending money from a wrong account is worse than a segfault, imo.