You can do this, it is useful, but it's just not the same as where the goalposts are now which is: the AI is a person in a box and can do everything a person can.

If we actually limit them to "only accepts tiny ultra well defined problems and ultra well defined outputs" then theycease being a $10T/year idea and become a merely $10B/year idea.

Thus, it is not exactly popular at the moment.