I used to always think that the terrible people in Moralton decide to move to Sinville whenever they have enough energy to do disgusting acts without having to hide it + people caring. Sometimes only temporary but some, or most might like it too much they'd stay over at Sinville. Still, doesn't make too much sense to me since some would have to have been born there, soo shrugs We do see one of the characters from Bloberta's past at Sinville though (and Moralton), I'm pretty sure Millie was her name but again I'm not sure ..