For years the most popular number of players a designer board game goes up to is four. Be it a tableau building card game, a German style point salad, or a full-blooded American slugfest, it seems that if it does not cap at two, it will go to exactly double that number. Why?
Let me start by saying that I do not have the definite answer. In fact, I don’t think a definite answer actually exists. However, since I am currently present at pretty much every step of development of each of our games (plus, I also include the pure design steps on a regular basis), I can definitely give you a few good reasons for opting to make most games “2-4 player”. Here’s a short list (in no particular order):
3 is both too few and too many.
Back when I was only making my first steps into the truly modern designer board games (which was around 2005-2006), one of the things that would frustrate me on a regular basis is that so many of the games I was interested me could only be played with a minimum of 3 players. Today, while we still see a lot of smaller games that start at higher player counts, it’s actually hard to find a Eurogame that needs at least three players.
The minimum number of players dropping to 2 is actually rather simple to explain. Board games (even the designer ones) have pretty much always been a family pastime. And since families today quite often consist of about 2 people (as evidenced by current household size, which is about 2.2 in Europe[http://ec.europa.eu/eurostat/statistics-explained/index.php/Household_composition_statistics], and about 2.4 in the USA[http://ec.europa.eu/eurostat/statistics-explained/index.php/Household_composition_statistics]), that’s where the number of players should start at.
Hence, a 2-4 player game can easily accommodate a (literal) couple of gamers who want to play on a weeknight (when inviting more people over might be difficult), as well as two gaming couples that get together periodically to play some games. This player count also comfortably fits most families with kids, allowing the still popular “2+2” model to make full use of their new cardboard acquisition.
4 times 3 is better than 4 times 10.
Simple symmetry is often an important factor in forging a good board game design. Allowing all players the same number of actions, making sure that each player is first (or last – whichever’s more important) in a turn the same number of times or having a number of cards or resources easily divisible equally between all players is often a solid foundation for overall balance.
With a 2-4 player game you’ll get all of the above at multiples of 12. So having 12 rounds, 24 wheat counters or 36 worker dice ensures the aforementioned base balance without having to create varied setup procedures, or allows to use simple calculations to remove some of the elements if playing with fewer than four.
If we were to do exactly the same for a 2-5 player game, the manageable 12 suddenly becomes a whopping 60, which means that balancing everything out (again, on a very base level) immediately becomes more complex, often forcing designers and developers to make concessions like having a perfect balance for 2 and 4 players, but not so much with 3 and 5.
4 is where you make a cut.
Preparing a game for production is always a balancing act: you want to put as much game inside the box, but you also want to keep the suggested retail price reasonable. In that context, adding another player means adding some base components (from another scoring marker and player aid, through to extra boards and whole sets of cards or resources) which are redundant when playing with lower player counts.
Deciding where to make the cut is always arbitrary, but (based on the stats you’ll find a few paragraphs above this one) it seems that when you stop at 4, you will still please the majority of people who buy your game. This is why it is now so common to see extra players added in expansions.
While I personally find adding extra player materials a bit of a copout when it comes to expansion content, the practice is rather widespread these days. Naturally, there are always always people saying that publishers should add the extra players to the base game, but I almost never see a lack of 5th (or 5th and 6th) player levelled against a game in a review or playthrough.
3 friends is all I have.
Finally, there is one more important matter: testing the game. With a 2-4 player game you can more easily nail down your balance with any player count than if you also needed to make sure that the design does not fall flat on its behind with an extra body at the table. And since designers and publishers often employ actual, existing game groups as testers, finding one that is larger is simply more difficult and time consuming.
And really finally, there is also the matter of some wave 1 playtesting, which (in my case at least) means sitting around with the people I know and game with to play my new design. And while I actually do have more than 3 friends (or, to be more specific, more than may gaming wife and 2 friends), it’s again much easier to make sure that I will not make a knob out of myself (and I will not waste time of our testers) by unleashing a game that’s clearly broken (with 5 players) upon the world.