about sloping roof houses
Answers
In the majority of the world, it precipitates at least sometime during the year, so people traditionally do sloped roofs because this way the water/snow goes down by gravity (there are some places where buildings do not need a roof at all, only ceilings). The slope of the roof depends on the frequency, the amount, or of the type of precipitation. Where there is snow, you need a high slope because of the geometry of the snow make it harder for it to slide. When it rains, you need less slope (5 - 15°), the important thing is that water stream fast enough not to permeate the roof material. With the modern materials, you can actually do a low sloped roof, but you still have to deal with leaves and stuff that eventually can end up on the roof, so builders most of the time do high sloped roofs just in case.
Architecturally, because of this need for slope in buildings, the ancient cultures have developed beautiful sloped roof typologies that most people find pleasant. So they prefer those for their own houses designs.