Why do so many streets end in walls or dead ends?

The short answer

The dead end is a boundary, not a mistake. The cul-de-sac belongs to the families who live on it — semi-private space where children play because through-traffic cannot reach them.

The families whose doors open onto the cul-de-sac share responsibility for sweeping it, lighting it, knowing who belongs and who doesn't. Strangers who enter are noticed immediately — not confronted, just watched.

For visitors, the dead end is a navigation problem. For residents, it's why the street is quiet and the neighbours know each other's names.