We have tented and Rv's in Banff and other locations in BC and AB and never had anything stolen.
Keep in mind that once you are on the Ice Fields Parkway, there are very few exits. If thieves are breaking into vehicles it is easy for the police to set up road blocks.
I would not compare the national statistics for property crime to that area. I certainly would not compare it to something that happened in Seattle, or Vancouver or Calgary for that matter.
Thieves are usually opportunists, in Seattle the thieves were probably looking for something they could sell to buy drugs. No place for either where you are going.