It hasn't always been that way actually. I worked apple retail while in college for 2 years, and we only had 'runners' to bring inventory up from the back the last 6 months I was there... and the white macbooks were released at the time the "Specialists" (salespeople) were responsible for doing the running themselves.

They did at his store - it's substantially faster than waiting

It is not faster than waiting, because there's no waiting. You do other things while it's being brought out, like trying to sell attachments to the customer or (in this case), finding out what the next student wants. Behaving inefficiently and adding traffic to the back on a busy launch day is simple incompetence.