I find this attitude baffling. If you bought a car or a phone and paid in monthly installments, you would want to know for how long you'll be paying, not just the monthly amount. Why is a mortgage different?
Is it the duration, where your brain sees 20-30 years, and substitutes that with "forever"? How would you feel if, after 30 years, when you thought you finally paid off your mortgage, the bank would say "Oh actually you have to keep paying for another 30 years"?