Souplex said:
Because scythes aren't weapons. They're farming tools. Only an idiot would fight with a scythe.
http://www.escapistmagazine.com/forums/read/18.70517-Scythes#694172
The real question is why do RPGs neglect polearms and axes? Historically they were the most commonly used melee weapons. Swords were the equivalent of an officers pistol.
Because of this attitude. Everyone looks down at the bare efficiency of a weapon, not the psychological aspects behind it. Think about it: You have someone come at you with a scythe, you can assume one of two things: They are either an idiot, or they are a bloody genius. Why the latter? Because the only person who could use such a weapon competently in combat is someone who is trained with it. Someone who knows dozens of ways to kill with it, and someone who chose it specifically for some sort of tactical advantage. An advantage You. Don't. Know. That's the most deadly weapon of all: The Unknown. That's the ridiculous thing about RPG combat, everyone thinks about the soldiers weapons, the generalities. Polearms, axes, crossbows, guns, even swords. Things that everyone used.
But that's not what made a man dangerous, the most dangerous warriors were the ones using weapons you didn't understand. How do you think net and trident gladiators even survived to begin with? That's not a common style of combat in the field of war, so it gave them an edge despite being strategically infeasible. If, and only if, you understood the combat style, it was easy to defeat, depending on what the net and trident are made of. But you face someone like that for the first time, and they actually know what they are doing? You are going to die. That's why education and knowledge are always your strongest weapons when fighting.