I work in a 100 person company and we have no dedicated Admin assistant, just a couple employees who act as receptionist, HR, office manager, and part-time admin assistant to the CEO. so 2% of our workforce falls under the "Admin assistant" role. If we didn't have extended office hours that needed two people to cover, we'd probably have only one person in that role.

So while Secretary/Admin Assistants haven't disappeared completely, there aren't as many as there used to be.