In India, the caste system is still strong in certain villages; those who believe in caste system do not use the utensils touched by other castes - especially by those from a "lower" caste. I have always tried to figure out what would have caused this behavior. Possibly obsessive compulsion towards hygiene was the root cause. Like every other best practice, the practice of washing the hands before eating and after touching any dirt became a rule and then became a rigid non-negotiable custom. Obviously those who worked in farms, workshops and those cleaned the town etc. had dirt in their hands after work and they became untouchables.
The western world that strongly opposed this behavior is slowly getting into the "custom" mode. I recently visited Detroit. An old lady who was working as sales person in a huge retail store (one of the big retail chains) threw her water bottle into trashcan as a child from a developing nation touched the bottle.
In another incident, an Afro-American tried helping a teenage boy who was about to drop a big pack of walnuts. The boy threw the whole pack because this person touched the pack! It was such a crude shock to me. It was not a shock to anyone else; they took it as a normal phenomenon. Probably it was a normal behavior for the medieval Indians too.
Hope western world realises this and tries correcting this behavior before it becomes so deep rooted.