In some countries there are weird (to us) cultural rules.
In Saudi culture, the left hand is traditionally reserved for personal hygiene tasks, and using it for public actions like eating, passing objects, or greeting others can be considered disrespectful.
*Gotta be careful shaking hands over there
In Thai culture, politeness and respect are shown through specific body language and actions. The head is considered sacred and should not be touched, while the feet are considered the lowest part of the body and should never be pointed at someone or used to move objects.
*When I was in Thailand it was reported our president had tapped their king on his head. A no-no