Managing remote systems is a time consuming endeavour. Aside from just standard maintance, other things are required to be an effective System Administrator. One of those is secure system access. It wouldn’t be good for you (or your client) if your System Admin password was suddenly common knowledge. Just like everyone else, System Admins tend to select easy to remember, short passwords.
Fortunately, there is a solution. When connecting two Linux machines together – whether its because an administrator is connecting to a remote system, or you are doing a remote back up (you do store data off site, right?) – the ability to automatically connect to another machine is a huge time saver.