Why? More reserve ammo, that's why. I just checked the armory to see if it was possible to roll any of the Armsday rocket launchers (JLB-42, JLB-47) with Field Scout, and it turns out they can't. I always loved having Field Scout on any rocket launcher than didn't have Tripod. It guarantees you get 2 rockets (or one magazine) every time you pick up a Heavy Ammo brick, or 3 if you pick up a crate in PvP. Everyone in PvP is using Truth anyway, and that gives you 3-4 rockets plus a 3-round magazine, tracking, and proximity detonation all in one package, so why the hell not?