My guess is that it's less about performance so much as reliability. I've had three incidents in the last two years which required connecting to a server that h

My guess is that it's less about performance so much as reliability. I've had three incidents in the last two years which required connecting to a server that had an out of control process pool that had exhausted pids. I also had a storage controller go and had to figure out how to use shell builtins to create a tmpfs and reflash the firmware. There are many reasons to provide builtins for basic file commands, from saving the extra process start to the tiny performance boost for scripts that should probably be using find instead.