About one out of every five home loans at three big Canadian banks are now negatively amortizing, which happens when years get added to the payment term of the original loan because the monthly payments are no longer enough to cover anything but the interest.
In addition to comparing against cost of rentals, there’s also opportunity cost with investing. If someone has a mortgage averaging 3-6%, and invests at 5-10%… that’s a great strategy. Why wouldn’t you push the amortization as long as possible?