Fluff gets such a bad rap sometimes as being 'simple' or 'low-stakes,' but that's missing the whole point. Knowing what fluff fundamentally is—those warm, comforting, happy moments focusing on intimacy and everyday joy—forces you to develop character voice in a different way. Without a big plot to hide behind, you have to make two people just talking in a kitchen compelling. It's about the small gestures, the inside jokes, the quiet understanding. That's harder than it looks.
I used to skip over fluff fics, thinking they were just filler, but trying to write one showed me how much you need to understand your characters' baseline chemistry. If you can't write them just being happy and relaxed together, how convincing is your angst later? It’s like emotional calibration. Getting the fluff right makes the eventual conflict or drama hit so much harder because the reader has something tangible to mourn or fight for.
It also teaches pacing in miniature. A fluffy one-shot is a complete emotional arc, often just a single scene. You learn how to build a mood, sustain it, and land a soft, satisfying ending without any explosions. That skill translates to every other type of scene you'll ever write.