So what? All you need to do is make sure the structure can support the weight of the added snow load. Which entirely falls under the rubric of "practicality, technology, and efficiency".
How is it efficient to make design choices that increase the strain on the structure, forcing you to add extra strength that would not otherwise be necessary?
It wouldn't be efficient if the only thing a flat roof bought you was added strain. But, for the most part everything is a tradeoff. Maybe the practicality of extra floor or head space is worth increasing the strength of the structure.
That's not all you have to do. I'll let people who've owned houses in snowy climates amplify that.
In a building, water is your eternal enemy. Keeping it out of places where it doesn't belong accounts for a good part of the other things you have to do.