Mustrum_Ridcully
Legend
I agree with this, and even back in 1e I avoided having NPCs use buffs (ie Prayer). Most 3e monsters are overpowered for their CRs anyway and they rarely need buffs; if anything their stats work better without buffs (eg a 3e dragon that buffs its AC can easily become unhittable), I don't get the impression the authors took buff powers into account in the statting.
Though beware: To some extent, buffs and debuffs are important to the game. But there shouldn't be too many of them, and most importantly: They should only matter in specific situations. They are there to "make a point" - to bring through an attack that needs to hit. But buffs that you just have running to keep the status quo are usually terrible. They provide no interesting tactical option, and after you have figured out that it's a good idea to give everyone a Bulls Endurance (especially 3.0 style), it's no longer an interesting part of the game.
It's a little paradox - changing statistics is awkward, and long-running buffs should be a preferable. But they are not. They just add book-keeping.
Buffs that stay interesting seem to be those that directly affect an end number - like "+2 to attack" or "+2 to AC" and don't interact much with others - keep the stacking consistent. Spells grant a spell bonus, items an enhancement bonus, for example.