Have you ever wondered if everyone else is crazy? Maybe it's some type of "lead poisoning" thing again, similar to what is believed to have helped destroy Roman civilization? Apparently it does make a quite different, the type of metal you use in your plumbing.
It has to be something like that. Otherwise, our only real explanation is that most of those nearly-hairless upright uptight barely-conscious hyper-active clothed monkeys are just completely whacked. That wouldn't bode well for the future of the species, would it?