That’s a hefty assumption. I don’t think it’s the norm though.
A paid off mortgage and no other debt is a retirement objective that has been achieved by practically every retiree in my family. I can only think of one who is still paying on a note. Things are different in low cost of living regions of the country. You can actually get out of debt servitude and live a reasonably decent life fairly cheaply. I have an aunt who has outlived her and my late uncle's retirement savings at age 99, and she's holding it together OK on Social Security alone.