You do know what "sidearm" means, right? It means that it's a last resort weapon for when your primary weapon, like an assault rifle or scout rifle, runs out of ammunition and you go to your backup weapon, a sidearm. That's how any solder is outfitted. At least usually, unless they have a special task like blowing off locks and opening doors, in which case they would also have a shotgun or something similar. I know I'm gonna be rocking one of those lovely sidearms in my secondary slot unless I'm doing something important that requires a sniper or shotgun.