It varies.

There are definitely cases where the latest update outright breaks the game and that is bad QC.

But what people generally refer to here are games with a modding scene. A vocal part of the userbase rely heavily on mods and/or custom DLLs. So when the game updates, all of those break until the modders and tool writers are able to catch up.

There are a lot of implications to this for games with (meaningful) online components. But for predominantly SP games? It is a fun time when you sit down to play a game in the evening and see it was updated and know you can’t go back to that save/game for at least a few days. And there very much SHOULD be a way to opt out or freeze a version for those.