(1) Typewriter keyboards were actually physically strenuous... find an old manual typewriter and type a couple pages on it and see how whether you feel like typing a dozen more. This was rectified beginning in the 60s I think, but manual models were still around for a while due to cost.
(2) Even once electric typewriters were invented, dealing with minor typos, let alone more major textual surgery, remained a huge hassle until the personal computer / full word processor came about allowing on screen editing... Just imagine typing most of a page only to realize you forgot a sentence near the middle, or even made just a small typo. which is around when typists stopped being a thing, because then, and only then, typing had become so automated that a reasonably skilled bureaucrat wasn't really saving much time (and losing latency) by using the typing pool, especially for brief, urgent memoranda.
It is a case of automation working so well, you don't even notice it at all and thus think nothing was automated, until you think about it in more detail.