Example: devs often see their game as a work of art, similar to a movie. They worked on it, crunched during development to get it done, and finally released it. It's done. They've moved on to their next project!
Sure, they might drop a patch release here or there to fix a bug in the game, but in many cases, games are effectively “unmaintained software” the moment they’re released. You can balk at that, or you can try to understand why some assumptions about software development might not apply.