For most users, it is easier to have one password for multiple applications that require a username and password. The users don’t forget the passwords as often if they only have one password to remember.
Security is increased for the company by requiring a more complex password, and if users only need to remember one password, they are less likely to write that password on a piece of paper and store it by the computer.
If a user has multiple passwords, the calls to the help desk increase because the users forget their passwords more often. The help desk must spend more time resetting users’ passwords.