I think it has to do with survival of the elements. In colder climates, People had to better protect themselves from the winter. They had to ensure their survival by building shelter that would withstand harsh winters. They had to grow food that could be stored so they could eat, they had to come up with ways to preserve food, Protect their livestock. They had to make clothes to keep warm This entails hard work. In warmer cliamtes all you needed was a grass shack shelter which could easily be rebuilt if destroyed from the occasional storm. Fruit and game are around all the time due to warm temp all you needed was maybe a small boat and pair of shorts.