Using Kentico Xperience's content locking is very important when you have multiple editors in a site, but when someone forgets to check pages back in, it can become a problem. We've seen many clients lose work because they chose to click the "Undo Checkout" button to get back in (you really never want to do that). If someone has good changes/updates, you will want them to check it back in.
This check reviews all the pages that are checked out, and lets you know if anything has been checked out for a while. If someone has something checked out longer that the default value (7 days), then it is likely checked out accidentally. This can lead to issues in the future. So, while the changes are still relatively fresh in the person's head, you may want to ask them to either check in their changes (or undo if it was truly unintentional).
Having this check turned on can encourage good habits of timely check-ins.