You sound like the passengers who stroll up to the gate at departure time and expect to walk right on board only to discover the door closed and the jet pushing.
Like the sign on the gatehouse counter says, "All ticketed passengers must be onboard 10 minutes prior to departure."
Just a heads up if you're flying with me. Show up AT van departure time, the first time, I'll wait for you and we'll have "the talk." The next time it happens, we're leaving AT the set time, regardless if you're strolling out of the elevator.
As far as international flying, you'd better be downstairs 10 minutes prior, because you're going to need to check out and that takes time.
You may think that I'm being a dick. I'm sure I am, but I don't care. I've decided I no longer care about anyone else's feelings.