Preventing frost from heaving the wall I suppose. Insulation on the outside of the wall is okay though.

I am not a concrete expert either. They may not want the concrette or block wall put through too many freeze thaw cycles. Your winters are at least as harsh as ours I think. Take into consideration that when your house was built the chance of the contractor ordering a mix that was better able to cope with the freeze thaw cycles as highly unlikely to non existant.

Cost of energy today though means any improvement is worth the effort usually. Plus it will make the floors on that part of the house warmer.

I have many thoughts about insulating concrete or block walls on the inside. A german bricklayer I once employed told me in northern europe they never insulated on the inside. He also suggested it was not the best ideal to do so in our climate in this part of Canada. . As you get further south in the United States these concerns are not as valid.