Because I just got shot in the back by a teammate at a COP after a loot room. Couldn't even catch his name as i had to respawn to try and get my kit back. Turns out he grabbed my kit and logged off. Bro is cold blooded, couldn't even stick around to troll and piss me off further. He just robbed me.
As there's no punishment at all for team killing, I'm just gonna blast the next dude who acts sus around me.
My point is, why is friendly fire even a thing? I can't think of a situation where it would add to the gameplay. Yes, I've played milsims where it's an important element to ID targets and properly aim CAS, however in this game, you have three methods of identification and its 100% clear who is a teammate and who is not. Referring to the compass on screen at all times, the eyesore of an armband and the map. Unless you're drunk, the only way to accidentally kill a teammate is by having incredibly bad aim.
In my opinion there is no added value to this gameplay element. All friendly fire facilitates in it's current state is trolling and stealing loot. And it's incredibly easy for the developers to turn off and improve the game.