Caught the Apple employee.

When most of this code was written, sandboxes didn't exist. Existing security concepts were built around protecting users from hacking each other on a shared multi-user system. Of course a user is allowed to patch their own processes, how else are they going to debug them and why should we stop them from doing so?

If you have Administrator access, you can patch the memory of anything...a normal user wouldn't be permitted to patch Explorer.

Trying to prevent patching in userland code sounds like a nightmare.

Because you're admin and you can do anything you want with that power good or bad.