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The Uchiha clan, as decreed by the tenets laid down during the formation of Konoha itself, lived by their own volition alone and isolated within their compound and not a single one of their clan heads had ever attended an informal meeting such as this one, preferring instead to state their business officially in the time-tabled council meetings. The official reason for such isolationism, according to the Sharingan wielders, was that as they ran Konoha's police force they had to appear incorruptible at all times and, though no offence was meant in any way to the other clans, potentially rolling out of a fellow ninja's clan house three sheets to the wind at some ungodly hour of the morning may have put a few doubts in the minds of those they were supposed to protect about their supposed unimpeachability. The unofficial reason, voiced by Akimichi Chouza's father when he'd had a good few tankards of mead in his belly, was that the Uchiha clan 'had so much wood up their collective backside that Shodaime-sama could have grown a second Konoha if they all bent over at once'.

Needless to say, though much less tactful, the second of these explanations was often considered to be the more accurate of the two.

The Mouse of Konoha, Chapter 10