It happens pretty often. $thing is installed, individual user accounts are created, and the default login is forgotten about. Nobody uses it, so nobody noticed

It happens pretty often. $thing is installed, individual user accounts are created, and the default login is forgotten about. Nobody uses it, so nobody noticed it. Another variation is not even knowing default accounts exist. i.e. where there is a CLI command to add a new user, which was done during install. This obviously isn't always the case - but it happens a lot.