Real world example: Mastodon would toss out and stop updating home feeds to save resources after a period of inactivity.

https://github.com/mastodon/mastodon/issues/5634

So people came back to empty timelines. Terrible UX, but until someone both experienced it and mentioned it, no one with code access realized how bad this was for returning users. Now there's a friendly message letting returning users know what's going on.