While I do agree in principle, that's not every group's playstyle. For example, I totally make up stuff on the fly, but major NPCs and villains are always statted out completely rules-legit. My players aren't great on metagaming, but they do appreciate the feeling that things are 'fair' on them. I.e., I don't make up stuff just to spite them. Knowing I play by the same rules as them helps make them feel comfortable with the game's general fairness and prevents frustration from time to time.
...but I'm not fudging anything or dream up weird stuff, so my group's content.