Why is 'compactness' valued? If a district should be people of a similar background/interests, then the geography is messier- the NC 12th district is basically

Why is 'compactness' valued? If a district should be people of a similar background/interests, then the geography is messier- the NC 12th district is basically the I-85 corridor, which may make more sense than a square of arbitrary size. If a district is just supposed to be a random container of voters to apportion representation, then base it on a voters' SSN or something and remove geography entirely.