your point is that there is no in-game reason. ZD agreed with you and gave you the most likely, even if cynical, out of game reason.
There is no in-game reason. They needed the class to stand out from teh rest and used a mechanic they have in another game. They couldn't use it for Troopers, as the "fantasy" for those is to heroicaly and unflinching stride into battle, guns blazing. The gunslinger/sniper are more aimed at people who, watching an action movie, will say "You know? If I was getting shot at, I think I'd get out of the way of the bullets..."