We have made-up space armour and energy shields. In fact, if we didn't, we'd die from the backscatter radiation produced by firing the made-up space weapons we use. Hell, there shouldn't even be a multiplier for headshots but I guess you can't make a FPS without it?

Dropsuits are tough, really tough.

Just firing a Laser Rifle without a dropsuit for even a small amount of time would give you a lethal amount of radiation if you aren't in a dropsuit. It would probably permanently blind you and give you 2nd degree burns on most of your body.
Firing a single round from an Assault Rifle while not wearing a dropsuit would set you on fire.
Firing an SMG causes enough kick to break the bones of someone without a dropsuit.
Scrambler Rifles/Pistols shoot laser-plasma channel induced lightning. I don't even want to know what would happen to an unprotected person if they shot one...

In fact, the only "safe" weapon for anyone without a dropsuit to use is probably the Flaylock Pistol, simply because if fires rockets and therefore has negligible kick. Even then, I wouldn't be surprised if their hands got burned from the projectile's rocket propellant.

Basically, our suits a made to take a beating.