but my thought was about ensuring that passengers travelled with their own luggage and that the person boarding an a/c was the correct guy, from a security point of view.
Surely the basis of that rule was the assumption that the security threat wanted to not be on the plane and thus survive. the people you are protecting against these days don’t care if they survive... that rule is pointless and 100% screening of luggage is done so who cares who is on a “domestic” flight.