This may be deliberate in some cases, e.g. banks who really want you to memorise a password rather than storing it in any way.
Storing passwords (securely, of course) is a good idea, and I think most banks would enourage it.
Storing passwords in some fashion that allows them to be cut-and-pasted rather than typed -- that is: storing them on the device from which the authentication is taking place -- is more questionable, because a password stored on the device could be captured by malware and used again without the user's knowledge.
Very long, very arbitrary, passwords are almost impossible to remember and retype correctly, and so are an indication that an on-device password manager is being used. Banks might reasonably object to that.