3 ideas
Divide 72 by the annual rate of return to estimate how many years it takes money to double. At 6% money doubles in about 12 years, and at 12% in about 6. This makes clear that a small difference in return rate compounds into a large difference in final wealth, especially over long periods.
Every extra dollar paid off a non-deductible home loan earns a guaranteed return equal to the loan's interest rate, and that return is effectively tax-free. To match it, an ordinary taxable investment would need to earn a much higher pre-tax rate. That makes accelerated repayment of the family home one of the highest risk-adjusted uses of spare cash for most wage earners.
Debt is judged by what it buys. Borrowing for assets that can grow in value or produce income, such as property or shares, can build wealth, and where the interest is tax-deductible the after-tax cost falls. Borrowing for consumer goods that depreciate costs non-deductible interest on something that loses value, so it should be minimised and cleared first.