Chess is a politically-themed wargame featuring monarchy. The King, being top kick, makes the rules of the land. Of course the King would enact such a rule that

Chess is a politically-themed wargame featuring monarchy. The King, being top kick, makes the rules of the land. Of course the King would enact such a rule that makes putting/leaving him in danger illegal. Think about actual, medieval monarchs in their castles, holding literal absolute power over everyone. If someone were to invent a board game featuring a King, and the King were to be made aware that you moved him into danger and got him captured, he might have your head.