... or
c) they are used to someone else teaching the theory and doing the briefing and expect you to step onto the pad, knowing everything already. Getting highly impatient if you don't. Also this guy was very impatient when I took my time for a thorough pre-flight inspection... He was used to someone else doing it for him, then just kick the tires, light the fires...
I had four instructors. Two civilian, two ex-mil. The only bad egg was one of the ex-mil guys and he was a retired military instructor. The other three were awesome! So 2-1 for the civies in my case...