Fundamentally, the reason we play games instead of rolling dice and doing math with the results is because games are emotionally stimulating. That is, ttrpgs produce emotional responses (whether the emotion in question is fun, fear, sadness, etc.) and we play primarily for these responses. The challenge of working out how to get the enemy's hit points to 0 is, in contrast, intellectually stimulating; the part where you're an elf and the enemy is a dragon is the part that makes it fun or scary rather than simply challenging or interesting. Without the narrative, the game becomes "component one performs operation thirty-seven, decreasing component two's attribute eleven from one-hundred and sixty-two points to eighty-four points." So, the narrative provokes the key emotional response that makes the game worth playing. Metaphor, as you probably know, is the among the most important tools that narrative has for provoking emotional responses (possibly the most important, discounting base sentimentality). A game that ignores basic understandings of metaphor (or a DM who doesn't understand the metaphorical frameworks they're working in) produces narratives that are dissatisfying on a subconscious level. This isn't the worst thing in the world, and I honestly think that D&D's flavor text does a fantastic job of implying its metaphorical framework for players and DMs. But having an understanding of the essential narrative at the core of a game you're designing and the metaphorical framework you're working in lets you design your game so that your players are incapable of missing the particular emotional response you intend to provoke, and that's the idea at the center of this thread.