People want to be able to kill each other in the fastest, most satisfying ways. This is why Heavy weapons are great. They want the same rules to apply to their Secondary. Skilled users of Snipers and Shotguns can get 1HKs with them. Fusion Rifles are basically RNG guns (you never know where they'll hit next) and Sidearms lack the punch of any of the aforementioned weapons. I like Sidearms and would like to see more of them, but ammo conservation only factors in in certain gamemodes.