Bungie wanted to remove weapons that ignored the ammo economy, specifically specials and heavies. While Icebreaker may not be the hottest pick in the D2 sandbox should it return, it still regenerates ammo which means you don't have to risk running around to obtain special ammo. It's a weapon that has the potential to be abused to become a problem. Its return would also make running double specials viable due to one needing special ammo and the other regenerating it instead.