You can probably tell from other posters already that this idea has been suggested numerous times before with no avail. Let me explain...
MCSG started back in April of 2012 with one goal in mind, and this was to create a game that would replicate The Hunger Games as close as possible. As you may know in the end of the Hunger Games there were 3 tributes left, Katniss, Peeta and Cato (A career), this is mainly the reason why there is still a 3 man deathmatch today. MCSG is not about wins, no matter what other people say, MCSG is a game to have fun with others and replicate the original Hunger Games and its trilogy of books.
Now about HiveMC... The Hive was not created solely for Survival Games, it was created as a mini games server with a few larger game types thrown in. The Hive is not intending to replicate The Hunger Games to a tee, rather they are trying to be different and stand out. If we simply gave in and put a 4 player deathmatch, MCGamer would not be as unique as it is.
I hope this clears a few things up, if you have any further questions feel free to PM me or a Moderator for more information.