I wash my hands, I can't see bacteria or germs, I've certainly never seen a anyone die directly because of unwashed hands, and it's just a slow statistical increase in sickness if a whole bunch of people stop...
but I don't wash my hands because I observed my elders, or because some cultural figure told me it was merely the way of our people. Some just told at some point to wash my hands cause otherwise people get sick, and if I had had questions they'd have mentioned germs and stuff.
Like did any one check if the Tukanoans know manioc will slowly poison them otherwise? I know it's a bit of a fuzzy line but is that process "tradition" or is it "technology"