It does seem a bit insane, but the solution is not always so simple. Many of these neighborhoods are built on hilly terrain, and there are many laws and regula

It does seem a bit insane, but the solution is not always so simple. Many of these neighborhoods are built on hilly terrain, and there are many laws and regulations about building roads, particularly building at a particular incline and building on stable and erosion-resistant areas. Most of these cul-de-sac layouts are aimed to maximize views and minimize construction costs, hence you have a sort of minimum-spanning tree configuration. Also, many of the streets are forced to follow isolines in the terrain.