Minecraft wiki entry for Curved_roofs, associated text: Domes are often seen in temples and other large, 'monumental' or civic buildings. Domes 'work' because in Minecraft one tends to assume a small symmetrical blob is supposed to be a dome even if it is actually quite angular. By comparison, other curved shapes are a lot harder to interpret, and because of this, they must be of much better quality before they look acceptable.