If the average mortgage currently is at 3% interest and possibly as high as 4%.
Then the national average for houses is 17% growth for the past two years....(which looks suspiciously like 36% over 2 years) then not paying off a mortgage is probably a good idea. Especially considering that mortgage interest and property taxes for a homeowner are tax deductible.
Also...your basic S&P index fund or ETF grows at 6%- 12% annually (depends on the year and this past year has been great)
Owning leveraged assets is a "no brainer".
Thats why the boom in real estate.
Speculators can buy several homes on credit and flip them a year later for a tidy profit every time. (So long as they don't pay too much outside of market rates for them)