One of the tasks of a WSUS administrator is to make sure that WSUS clients are up-to-date. This requires the WSUS clients to report to the WSUS server on a regular basis.
So if clients do not report to the WSUS server, you need to investigate and resolve the issue.
This script will show you which WSUS clients haven’t reported in X days:
Another use case would be if you manage a WSUS infrastructure with an upstream server and multiple downstream servers for each customer. If one or more 3rd parties are responsible for managing the WSUS clients, you could use this script to automatically mail them the clients they’re responsible for that haven’t reported for X days.