Why limit this to AI? There have been lots of programming tools which have not been universally adopted, despite offering productivity gains.
For example, it seems reasonably that using a good programming editor like Emacs or VI would offer a 2x (or more) productivity boost over using Notepad or Nano. Why hasn't Nano been banned, forbidden from professional use?
For example, it seems reasonably that using a good programming editor like Emacs or VI would offer a 2x (or more) productivity boost over using Notepad or Nano. Why hasn't Nano been banned, forbidden from professional use?