All that the 50-move and threefold repetition rules do is permit one player to claim a draw; the game may continue if both players wish to play on. (It has happened, particularly threefold repetition where the repetitions are spaced far apart and the players don't have much time.)

There are actually new FIDE rules as of 2014 or so, where after 75 moves, or a fivefold repetition, the game is immediately declared drawn without the need for a player to take action.