Guys that do that (dive into the van) have PPD- Pilot Personality Disorder. An estimated 55% of pilots have this ailment, btw

That scenario has caught me off guard a few times as well-- I would arrive in the lobby 5 minutes prior to van departure time, and on the hour I would call up to the captain's room to make sure he didn't miss an alarm... Only to discover that he's been sitting in the van the entire time, waiting on ME.

I chalk it up to rudeness and selfishness.