Being able to use throwable and shoot out windows from certain cars

There are a multiple vehicle games with lots of potential variations. Why can’t passengers shoot from windows or throw grenades out from bed of truck? Or being able to shoot zombies off the windshield of a car with a shotgun! Maybe being able to have a full vehicle of npcs or friends being able to shoot out the window, drop a grande or c4 at high speeds. Being able to use a shotgun point blank to kill a feral on your window. Maybe have a friend being able to shoot out the back of an open van or drop mines? Maybe even supplies?