I think it's because fusion rifles are really OP when you use them right. It's a good idea, but I can see why bungie did it.
English
-
Nah, with the Gozen-C and certain Preacher variant shotties the other secondary weapons all provide insta-kills given their unique situation.
-
Though true, fusion rifles offer longer range, and a cool effect to confirm a kill. Shotguns may be cool, but new stuff is cool[i]er[/i]