It's the zero/one/infinity rule. Programmers don't even know what it's called, they just absorb it by osmosis. But in the real world there are so many lists that will never have more than 20 items.
Well, I'd say the rule should be upgraded as zero/one/small-sample/expand-for-infinity, at least for user interfaces (not for coding, although doing it for coding is what lazy evaluation is for).