"Having everyone knowing how to read and write is the opposite of specialisation. It's inefficient and pointless. If a certain profession needs a document, it's much more efficient for specialist scribes to consult with domain experts, write that document, and sell it into the industry. Having every (for example) doctor being able to read and write adds negligible value, and I would argue the opportunity cost is awful. If my doctor has a choice to become a very mediocre writer or a better doctor, I would hope they choose the latter.
A society of part-time readers and writers would do nothing but produce a lot of badly-written texts. What's the point?"
The comparison with literacy is incredibly apt. Even though very few of us moderns are professional writers, we all benefit by knowing the basic abstractions of letters and words. In the future, everyone will benefit from knowing basics of computation. Probably in ways we can't imagine now, just as an ancient Egyptian scribe could not have conceived of "commoners" writing YouTube comments or texting "whatup u?" to a friend.