Why should you configure different admin passwords for all your routers and switches?

What will be an ideal response?

You are not doing yourself any favors in terms of security if all of your routers and switches have the same admin password. Having different passwords adds a layer of difficulty before the potential attacker. If your network administrator from the New York office quits, then you will only have to change the passwords on the routers and switches that she had control over, rather than all of the passwords. If a company is running multiple locations and using one global admin password, it is unlikely to change the password globally, as that is a big hassle. This is not proper security policy, but it is how the real world works.