From my experience, plants (whether in office or at home) attract bees, wasps, mosquitoes and other such annoying nonsense, that tries to bite you, stab you or enter your ears/mouth, and in office, flamethrowering them away with lighter and deodorant is not always an option (due to people not used to fire being afraid of it). Therefore, plants near me usually directly decrease my happiness and productivity.
(EDIT: I'm dead serious here)