Monster Hunter only allows for 4-player co-op so that each hunters input feels relevant
Have you ever wondered why the Monster Hunter series limits its hunts to only four players? Did You Know Gaming revealed that in an interview with Game Informer. Series producer Ryozo Tsujimoto explained that by having this limits, each player would feel like they actually had an impact on the outcome of the hunt and that by doing hunts together, each player grows as a hunter.
This feeling would have been lost had Capcom allowed for an army of hunters to hunt at a time and may have also led to some players letting everyone else do the work for them. This would have caused those players to become stagnant as hunters, and so every monster in each games online mode is made with four hunters in mind, and this limit has carried over to every game in the series.
This focus also extends to the rewards, which are also balanced with four hunters in mind because “if they’re distributed evenly, veteran players are more likely to encourage newcomers to contribute during the hunt,” to quote Did You Know Gaming’s video.