And when the Marine misses and the target is shooting back, the Marines just goes, "Oh well, I missed, I guess I can't shoot at him anymore"? When you miss, you shoot again.
I get what you're saying, but I can think of situations where the opposite is true. The ammo dice make sense in a situation where
1) You are in close proximity of the enemy and vulnerable (higher stakes situation)
2) Returning fire when enemy initiates fire contact (should be standard drill for most armed forces)
3) You are providing suppressing fire/trying to achieve fire superiority.
But they do not make sense in a situation where
1) You are initiating the fire contact with enemy (be it whatever context, but you just want to try and pop one guy and bugger off - hit and run tactics while saving ammo)
2) You are at longer range/in cover and can dictate the pace of the battle
3) Squad/team is providing line fire (not certain on the term, but in infantry tactics when the whole unit is popping off shots one by one after initial contact in order to keep the enemies heads down without going red on ammo in a second)
That being said, anyone can interpret the rules how they want, but if anything I think the ability to be limited to a single shot could be tied to the coolness under fire check in order to nerf the benefits of not straight up wasting your ammo. And for single shot weapons dividing the ammo dice up or something along those lines would make sense for me, if anything panicking with a bolt action or similar weapon would make your fire rate slower rather than faster.