Why learn to read and write when everyone carries a computer capable of TTS? Why learn anything when your pocket computer has access to AI doing the thinking much better than the average highschooler and has 100x the knowledge?

Because learning to read and write still develop your mind and capabilities. memorising stuff does not.

A better analogy would be "why stop memorising long works now we can read things instead". No one memorises epic poems anymore but we read novel instead.