talking out my ass, I’m guessing its because oxygen is an energetic and highly reactive element, and therefore it can do lots of things and it does them really well (or at least strongly), or in general was just the best most direct means to accomplish the energy intensive tasks that were required given the biosphere we evolved in? I’m not sure how common/ vital oxygen consumption was before that one mass extinction where algae became overabundant and oxygenated the atmosphere and caused a mass extinction, it could have been a result of adaptation to that new condition- though I doubt this is the case