You won't necessarily know about every leak. If a security camera records you typing in your password (or you accidentally hit view password in your manager) to

You won't necessarily know about every leak. If a security camera records you typing in your password (or you accidentally hit view password in your manager) today someone might find that recording and access your account two years from now. Resetting your password resets the buildup of these small information leaks that occur over time. Best practices get better over time. Maybe two years ago that password was stored as an MD5 hash, and that hash was getting leaked to log data. Bank.com has since fixed that problem, but you don't get the benefit unless you change your password.