You can discharge the battery to power the heaters, at significant cost in energy. The temperature becomes a serious problem when charging (will physically destroy the battery through dentrite formation!), and under very high power draws (battery can’t keep up chemically).

It can be solved, but at a cost, and makes the tech much more dangerous - you could end up in a situation where you freeze to death somewhere more easily in the climates it is a problem.

It’s similar reasons why diesel isn’t a great idea in Alaska and the like too, and people tend towards gasoline even in situations where it is more costly and less efficient (like industrial trucks). It can be mitigated with chemical additives (‘heat’), tank and block heaters, etc. but has similar risks.