Why does the military only allow 2 weapon attachments?

Sounds to me you play too much MW2. We don't use ACRs, at least not yet, we use M4's. Mine came with a M68 CCO and I purchased an EOTech that I put on it and I was issued a Surefire flashlight that I attached to it. It also had a vertical foregrip. That's all I really needed. A suppressor? What's the point of having one when we roll up in humvee convoys? Everyone knows we're there. They can hear the 6.5L turbo diesel.