Exactly this. I’ve spent my career working in market research and advertising, so I don’t have some of the same administrative responsibilities of some other fields, like medicine.
But, when I started my career, in the late '80s, a full staff of administrative assistants was the norm; each administrative assistant at the companies for which I worked probably had three to six people with whom they worked (unless you were in senior management, and then you had your own assistant).
At that point, few of us had computers on our desks; we would hand-write or dictate (on a Dictaphone) memos and reports, and our administrative assistants would type them up for us. But, within a few years (i.e., early '90s), nearly all of us had been given computers, and increasingly, we were at least typing our own stuff. The administrative assistants still did a lot of work, however: scheduling meetings, printing and distributing reports and memos, scheduling travel, etc.
When I started working in advertising, in 2000, we still had administrative assistants, though each of them had larger groups of people for whom they were responsible. By then, the assistants weren’t doing much typing (except for those who worked with some agency vets, who still used Dictaphones), but they were invaluable for scheduling meetings, arranging travel, filing expense reports, etc. I had the same assistant for nearly all of my twelve-year tenure at that agency, and she was awesome – she’d been there for a long time, and knew how to get things done, and who to call when there was a problem.
Now, at my current agency, there are nearly no administrative assistants left (only the very top management has them). All of those tasks are now the responsibility of the individual employee, and if one needs assistance or guidance on things like booking travel, filling out your timesheet, etc., it’s a complete snipe hunt to identify how and where to get help, and is made more difficult by the fact that the agency has offshored the support functions for those systems – for instance, all of our expense reports are processed by a group in Costa Rica, and emails which they send to us when there’s an issue with an expense are usually cryptic, in an ESL sort of way.
The OP mentioned mandated training, as well. In the past, there were a couple of mandatory training sessions which we had to attend (such as a course on combating sexual harassment), which were always in-person, and actually kind of engaging and interesting. Now, all of the courses are online / e-learning, and there is a ton of them, which we are all mandated to take every year. I have to sit through 20+ hours of training courses every year (harassment, data privacy, anti-bribery, etc.); they’re clearly important, but it’s also, I am sure, a matter of CYA on the part of the corporation.