Because in a hectic game like Battlefield, nobody likes getting instantly killed by things they can't even respond to. That's why sniper scopes have a glint as well.
And thats why medics have trophy systems that destroys the grenade and speaking about getting killed by grenades what about M320(also gets shut down by medic trophy system)
Neither the medic or any of the other classes are going to sit on a trophy system all day. It's a completely unrealistic expectation.
The M320 doesn't have nearly as much AOE as a grenade. It's strong, but not because of the damage potential. It needs a minimum arming distance, but other than that it's fine.
