I dunno, eyeballs are pretty much unitaskers. Vision gets used to help reinforce balance, reflexes, and proprioception, but that's all in the brain.

Teeth might be debatable. Arguably they're only for masticating food. The debate opens up whether other functions are physiological and so compulsory, social constructs, or neurological things we do instinctively.

With everything else, I 100% agree. It's all an engineering nightmare to service and troubleshoot.