That's a fair point, for many scenarios this stuff doesn't matter, like a video-game. However, most apps fall into either the "serialize a bunch of crap to disk

That's a fair point, for many scenarios this stuff doesn't matter, like a video-game. However, most apps fall into either the "serialize a bunch of crap to disk" category, or the "multi-user data changes all the time category". Nearly everything in the second category works best with a proper database.