People want to be precise, even if the situation does not call for it (even, in fact, if being precise works against the goal); give people a range that includes three options, and they will try to add more. I've seen this happen most with hiring, where people apparently cannot stick to yes/no/neutral assessment of a candidate, but must add "yes, but..." and "no, sorta..." options.
I've also now seen it with scoping. When we make our first pass at how long a project will take, we assign small/medium/large effort estimates to each task--or at least we did. I see that we have now added "extra-large" to the list of estimate options.
I'm not at all sure what this says about people, but I find it fascinating.