For one, I think Sha Do hit on something very basic; people taking fire return fire. Unless you have some very upgraded gun and know you have to switch to another weapon when closing (highly upgraded BA rifle, for example), someone with a stock-ish M4 taking full auto fire from an MP7 is going to fire back. That, I believe, is where the need for a uniform minimum engagement distance rises from.
Bogging people down with MORE rules and more stuff to keep track of in the heat of the action isn't going to help anything, and in fact is probably counter productive; rules need to be simple and clear and easy to remember/follow, even in the middle of a pitched firefight.
Originally Posted by MADDOG
My feeling on the issue is that if people would wear the face/ear protection that comes with their goggles, mercy distance would be a non-issue at any FPS."
Except many (most?) people aren't using paintball goggles, so they don't have a mask anyway. Even back when I did use pball goggles, I didn't use the mask portion; it's uncomfortable and blocks airflow and prevents being able to aim properly (arguably MORE dangerous, if you're "using the Force" to aim and hit the other guy in the face or groin, instead of the chest, in the process). Also, I stopped using paintball goggles specifically because I didn't feel they were as safe as real ballistically rated goggles around higher powered guns, and I would refuse to play using paintball goggles around anything but very stock-ish powered guns (300 fps).