Small neglected problems recruit companions.

One neglected thing signals that neglect is acceptable here. The pile grows next to the pile, the unaddressed problem makes the next one easier to leave, and the standard set by the first item governs everything after. It is not that disorder spreads mysteriously; it is that people match the existing level. The first instance sets the norm.

When something has been left, deal with it while it is still singular. In a shared space especially, clearing the first item prevents the accumulation rather than removing it. The earliest intervention is by far the cheapest.