What's the reason for this specific “rm” sequence in the xkcd joke?

Question

Here's part of this xkcd comic strip where the idea is that the author can't write a sort program so he adds code to delete all files

system("rm -rf ./");
system("rm -rf ~/*");
system("rm -rf /");

AFAIK the canonical way to delete everything is to rm / so that everything starting from root is deleted. Here this is the last command and the two commands before that try to rm the current directory and the contents of the home directory.

Why not just rm /?

Answer 1

If you start at the very top, it's possible that you'll wipe out something that rm (or some other critical part of the system) needs to continue, and the evilness will be left incomplete.

These commands will make sure that at least the cwd and the user's home directory are gone before going nuclear.

Answer 2

Just to show increasing levels of destructiveness: Delete the current directory, then $HOME, finally destroy all.