Mmm idk why either. Evolution is not proven as no one kept apes and see it grow into a human. It doesn't really make sense too. Animals don't have moral judgement, and can't create and understand images of art and drawing. It is weird if apes somehow adopts the abilities and become a human.
When coming to building something, some materials are more vulnerable to water and can wear away easier. Some can keep the water in, so depending on the material, the water quality can be better sustained.
