Not denying that caffeine addiction is real, but I also think "lack of coffee" has become a sort of blanket excuse for just being sleepy or not fully energized, regardless of the actual coffee intake. It's a common thing to just say, sometimes as a joke and other times as a convenient lighthearted excuse when someone misses a social cue or does something silly: "Sorry, haven't had my coffee yet!"
And most people who hear it kind of get it as well. They don't _actually_ think this person is physically addicted to caffeine. They hear it with the understanding that this person is just a bit tired, distracted, or out of it that morning/day/whatever.