The more obvious reason is that colder places do not get as many freeze-thaw cycles. It simply stays frozen for a few months. In contrast, much of the northeast experiences many more freeze-thaw cycles since even in the winter it is warm enough to thaw the ice on some days.

Cold places see a lot of freeze-thaw cycles in fall and spring - before and after the hard freeze. I don't know how they compare, but it isn't clear cut.