For example, what happens when an employee leaves and the employee was featured in a public-facing image?
One option is removing the image and replacing it with another. A second option is sometimes possible and that involves Photoshop and some Hollywood-style digital updating. The wonders of Photoshop make it entirely possible to extract the departed employee from the image and fill that 'space' with background content. Or the former employee is removed and replaced with another employee. This may require a new photo with some attention paid to replicating the original settings. On occasion, replacing just the face is possible.
Where is the original version of the home page? What happened to that powerpoint slide we used in the video? How do we update the video? a web page? an image? Which logo did we use and where is the original jpg or tiff?
Other times, the issue is a water bottle left on a desk, or sloppy looking wires in the background that are a distraction from the main subject in the image. Objects can certainly be 'removed' or replaced. This is a frequent issue with logos, often brought about with a change in vendor.
Maintaining a site can be as simple as making sure that a 'snapshot' of a website is taken and stored on a thumb drive or CD for safe keeping. For a video this is verifying that media (e.g still images, and audio files) are saved along with the original video files to the now ubiquitours thumb drive and safely kept as backup.