* What is a cooperative abstract game?
A cooperative game is a game where players must work together in order to achieve an objective, instead of working against each other. I am not referring here to "co-op gaming," which is when a video game or computer game allows more than one person to cooperate in fighting against an A.I.-based opponent.
An abstract game is a game which does not try to simulate anything. Chess is a well-known example of this: the pieces, the board and the rules do not actually try to simulate war. Abstract games usually rely on their simplicity and elegance to hold attention.
* Why are there so few games on this site?
The simple fact is that there are very few cooperative abstract games. Most cooperative games are for children, and virtually all abstract games are competitive.
I think both parts of this have the same origin: we believe only children deserve to learn and practice cooperation, and we assume adults are too "grown-up" for such "immature" (i.e. cooperative) things. This is absurd, because games do not have to be "mature" in order to be pleasant or fruitful games. It is also absurd because cooperative games can have great depth and complexity, as much as "mature" (i.e. competitive) games.
But another part of the problem, which cannot be underestimated, is that cooperative abstract games are harder to design in general, partially because there are no examples or principles to follow. This is one of the things I am trying to change with this site.
* A cooperative abstract game is pointless. You might as well play alone.
This is a popular but lame argument, since it equally applies to competitive games. You could set up a game of Chess and play as both sides, winning by Fool's Mate, and thereby declaring that Chess is pointless. The point of any multi-player game is in the interactions between the players, and saying that one can play them alone is technically true but irrelevant.
This argument is popular because competitive games are well-known, and we come to believe that they are the only valid form of play. In competitive games, it is the players that provide the challenge to each other. In a cooperative game, this element is excluded, making it appear as if there is no challenge. But the challenge comes from the game itself, either the game's structure, or some kind of time constraint, or both.