> A bigger shift is that now I only see CEOs or at most CxOs with secretaries. Mobile phones and Outlook calendars have largely wiped out that profession.

Depends heavily on the field. Most fields don't use the term "secretary", but e.g. my mid-sized company of several hundred employees has a single executive assistant, vs. my wife works at a law firm where it's pretty close to 1:1 professionals to assistants.

Probably because law is organized around billable hours.