[snoozer]

The question strikes me as a link-baiting deliberate obtuseness. If we're in a post-industrial age, why do we still have factories? If my Mac is a "personal" computer, why can other people have accounts on it?

"Post" means "after". It usually connotes some sense of replacement, but does not necessarily imply wholesale obsoleting of the thing that came before it.

I think "post-PC" is a calculated marketing term, but to criticize it based on the most absurd possible interpretation is, well, absurd.