The half-move counter in the FEN takes care of the 50/75 move rule. You do need the history if you want to implement the threefold/fivefold repetition rule, but

The half-move counter in the FEN takes care of the 50/75 move rule. You do need the history if you want to implement the threefold/fivefold repetition rule, but it's rare that it is actually relevant for e.g. a chess engine's strength.