You're right, you definitely don't want giant snow piles on your roof of your house, and yes, sloped roofs will help you avoid giant snow piles. But you still

You're right, you definitely don't want giant snow piles on your roof of your house, and yes, sloped roofs will help you avoid giant snow piles. But you still often end up with some covering. Not 100%, but I think high enough to meaningfully affect the cost-benefit calculations. Not to mention large commercial buildings with flat roots.