you don't "always". The mortgage industry has a long history of different optimal strategies given different scenarios. For example, overpayment and payment hol

you don't "always". The mortgage industry has a long history of different optimal strategies given different scenarios. For example, overpayment and payment holidays without incurring penalties used to be features only available on tracker mortgages. Discounted (yet still fluctuating) rates used to be effective. Fixed rate mortgages are popular with people that don't want to take on the risk of payment fluctuation as well as in economic environments such as today.