The relative weakness of the pieces in shatranj may have made this form of a win desirable.
This situation, called a "Medinese victory" (because in Medina, it was still a win for the player first baring the opposing king), was often considered a draw.
[4] Under modern rules, a player with a bare king does not automatically lose and may continue playing.
A bare king can never give check, however, and can therefore never deliver a checkmate or win the game.
A bare king can in some situations play to a draw, such as by stalemate, capturing the opponent's pieces to reduce his advantage to an unwinnable one or if the opponent of a bare king oversteps the time limit.