I think the answer to why is that when you hit the end of a quest, it wraps. It doesn’t mean everything wraps with a neat bow, but you are done. You have connected, the apotheosis happens/did happen, etc, etc. The XP pacing is a way of saying: “let’s luxuriate out in this quest and let it take a long time before we wrap”

I think that if your players are hyper efficient at pushing play to hit quest goals/5-XP bonuses, you could end up feeling like 25XP is too short for certain quests. But it’s good to recognize when that happens and find the exceptions. (also, you can just stretch out a quest goal mid quest, which is not even necessarily a penalty!)

And I think most players start off not pushing the “my job as a player is to get all the XP as fast as possible”, since it seems so emotionally different from a lot of games.