There are quite a few Canadians who live close enough to, or travel across the border often enough that their personal phone/number is from a US carrier, usually the closest town or city to their own. Depending on how often or how you use your phone, it can be half the price of having a plan with a domestic carrier. As far as I'm aware, most of the US carriers only require that the device registers on their home network at least once every six months, and bills to a US address, meaning even just a semi-annual shopping trip to somewhere like Port Huron (where you can also purchase a PO box and therefore have a US billing address) can save you hundreds every year.
To add some more context, their excuse for high prices and mediocre service is generally something to do with the size of the country, which granted they aren't exactly wrong, until you realize that roughly 90% of the entire Canadian population lives within 160km (100 miles) of a US border. Canadian telecoms are a legal cartel, for all intents and purposes.