Question

Why do homes in Sweden and Norway have steep roofs?

Answer 1

Its mostly a stylistic choice although at one points it was mostly a heat related idea. Hot air rises so having a steep roof allowed for the accumulation of hot air. It was also a good windbreaker so a collection of houses were able to stop a lot of the harsh wind from damaging things.

Answer 2

Sweden and Norway, both of these countries have a very severe cold climate and snowfall is a usual for them.

In areas of heavy snowfall, like Sweden and Norway, flat roofs would be loaded with a lot of snow which may cause some loss to the roofs and may lead it to crack.

So these steep roofs do not allow any water or snow to accumulate on the top of the roof and makes it easier for the snow to slide off it.