It's a significantly harder game. Computing a Nash equilibrium in a 2-player game is relatively straightforward in technique (albeit very computationally expen

It's a significantly harder game. Computing a Nash equilibrium in a 2-player game is relatively straightforward in technique (albeit very computationally expensive in the case of poker). There's several factors that make even 3-player games much more complicated than 2-players. An additional player requires some sort of modeling of the interaction between players, which may not be feasible. For example, Player A may have multiple co-optimal strategies with respect to his own EV, but that affects the EVs for players B and C differently. Player A can choose arbitrarily between these strategies at any frequency, but players B and C can't predict this choice at all. On top of that, Nash equilibrium requires that each player acts independently in their best interest. Teams can be modeled as a single player if necessary, but shifting alliances over the course of a series of hands can't be easily. And on the pure computational complexity side, the state space explodes when you can have more than one opponent in a hand simultaneously. Combinations of players in a hand scales as n!, not n.