The town is quiet because of Papyrus' habit of ruling it with an iron fist, instilling a curfew among other unsavory rules; if a monster appears weak, that monster is to be killed. If a monster disobeys one of Papyrus' rules, that monster is also to be killed. The citizens of Snowdin shun Sans (with exception to Grillby) since he is the brother of Papyrus, although he seems to spend the bulk of his free time there regardless.
Snowdin appears dark and unfriendly due to the houses' windows not emitting warm light, but dim, gray light. Because of Papyrus, Snowdin is most likely filled with copious amounts of deathtraps and dangerous puzzles to keep Snowdin's occupants from becoming too lazy or complacent.