I rode the bus in Alaska. The buses ran well below -50f. It turns out that it's not that hard to keep your batteries and oilpans heated if you bother putting plug-in heaters (literally, electric blankets for the purpose) in your fleet vehicles, winterize your vehicles, and plug them in when it's cold.
I get that it's uncommon to be that cold-prepared in places that don't expect to see temperatures below -20 for more than a few days in a given calendar year- at some point, it makes sense to just call it off when it's that cold. After all, do all (or even most of) the kids have proper clothes to deal with real cold?
Really cold weather can be adapted to, it's just that when you don't need it that often it makes sense not to spend the resources doing it.