Earlier quoted context omitted.
Banks make money on interest. Perhaps the principle itself is the issue, if it's legal to earn money on loans, no surprise a bank incentive is to make you take loan, and have you keep them for as long as it can. Typically a mortgage does not allow over repayments. Why? It would get people in the nasty habit (from the perspective of the bank) to pay back a little more every month with the spare they've got. Of course…
Mortgages have amortization schedules, Banks love it when you pay more as it only reduces the tail end of your loan. You still pay the interest up front. Not all banks are the same, some have other incentives to pay off early.
Only credit unions and small regional banks still hold mortgages on their books. The overwhelming majority(90%+) of mortgages are agency - ie sold to the federal government.