If performance is too bad, you can only use the shell for toy examples, which means there's no reason to have a real shell at all and you might as well go back

If performance is too bad, you can only use the shell for toy examples, which means there's no reason to have a real shell at all and you might as well go back to COMMAND.COM or equivalent. It's taking the idea of Unix-style scriptable shells and Improving the implementation to the point of unusability.