Chess sets used in tournaments provide the standard 16 pieces, plus an additional queen, so that if a pawn promotes to a queen, it is readily available to be used.
What happens if more than one pawn promotes to a queen and a third queen is required? Can a player walk to another game and look for a surplus queen? Would they stop the clock and seek assistance? Would the answer change if it were a blitz game?
Also, here, in a non-tournament game, Hikaru Nakamura uses a pawn because the opponent has the queen in his hand and the clock is ticking (although that's for the first pawn promotion, with his queen already off the board and presumably a regular chess set, not a professional one with an extra queen).