I don't know why banks are not replacing the many rusty and damaged coins that are circulating. Maybe it's because the banks are being very frugal with ordering money due to budget issues (makes sense, since traffic is currently in decline), and/or the banks are preparing for the demise of over-the-counter teller service, in which the affected branches will have cash in ATMs only (and ATMs are obviously not going to dispense anything less than $5 or $10 bills). But with crooks using stolen construction equipment to damage bank branches and steal ATMs (it started in Eastern Newfoundland, and now recently reported in Toronto), the future of ATMs may eventually be in limbo too.
It was reported on CTV last fall that Scotiabank is discontinuing over-the-counter teller service for some branches this year. One branch each in Ottawa and Nova Scotia are confirmed to be affected. The Ottawa branch will keep the ATM on site, but unfortunately it won't have anything less than $10 bills.