Why? We can't use it for GV training anymore. We used to be able to teach others how to disable/kill other vehicles. Now we can't. When you deliver a shot that would have taken out an engine or turret, you just die. It is impossible to test/train when you can't see the true effects of the shot.
The solutions offered by others (to work around this problem) don't work. Setting up a h2h arena is impossible without specialized networking knowledge/equipment. I've spent days trying to do it and despite all of the well meaning helpers, can't create an arena that anyone else can join.