If you are in a 1v3 for example and they are using guns that 3 shot you it wouldn't be hard for them to at least land 1 bullet each which would kill you. If they had guns that killed in 4 or even 5 shots to the body you would actually be able to take a few shots and live. Combine that with you hitting headshots you would more likely win the clutch.
@KruijtDennis Limb multipliers alone is a big deal imo, the gunplay is in such a bad state that little tweaks will go a long way. From what I was told by people in labs they did increase spread and headshot dmg too.