Chess manages in practice to be a game of imperfect information, like poker. Obviously it is explicitly a game of perfect information on the board, but the hidden information is all psychological. For instance: "do they actually know this opening/endgame? do they see a tactic? did they take a long time because they calculated that it's a good move, or are they bluffing by making it seem like they calculated something? are they actually better than me or just acting like they are?". etc.

It's true that "bluffing has minimal value against best play", but no human is in that situation. Even super-GMs will play "bluffs" if they are behind (or playing a lower-rated player and sure they can recover later. or just for fun if the stakes are low).

And that's not even mentioning optimal strategy under time pressure. For instance some of the Lichess tournaments are structured such that winning fast is more valuable than winning slowly because the resulting score comes from how many wins you can get in (or in other cases, how big of a streak you can get). So people will play in a way that optimizes for winning quickly by taking big bets / bluffing / creating chaos with un-calculated gambits, especially if they have a good reason to believe they're better than their opponents.