I've wondered the same thing. I think the cost difference might be an important factor. Secretaries were generally paid a lot less than managers. This was also

I've wondered the same thing. I think the cost difference might be an important factor. Secretaries were generally paid a lot less than managers. This was also tied into status. Outside of the military, typing was often seen as women's work, and below the status of a manager. There was also a much bigger need for typists back then, as much more correspondence was done through the mail. For example, you might write a draft on a typewriter, add hand-written notes with corrections, then retype to get the corrected version to send to your customer. Computers reduce that overhead. One of the organizers of a scientific meeting I regularly attend says it's harder now to organize the meeting than when he started. It used to be that a company included a general service component to one's job, which could be used to help organize a conference, or review papers. Now, the organizer said, companies want employees to be more focused on the bottom line. But at best those are hints. They don't answer your questions.