Rewind to 2006. Should we implement Python in Python? Of course not; it's not useful! PyPy should not be done! It's literally 50 times slower than CPython! For

Rewind to 2006. Should we implement Python in Python? Of course not; it's not useful! PyPy should not be done! It's literally 50 times slower than CPython! Fortunately, the PyPy folks have stuck with it, and PyPy is now faster than CPython across the board. Many other languages have also been implemented using its considerable infrastructure. Compiler experts have been minted from scratch. Should it have been done? Yes. Even with the vulgar assumption that "practical utility" is the only source of good, this type of project is good.