I think another reason for not using them, other than those above, is that we tend to sight in on specific targets with ease. In the war, the lead plane usually sighted and the rest dropped their bombs on his signal bombing the area rather than with the pinpoint accuracy we enjoy. By everyone targeting specific targets, that alters their course so they can not maintain formation integrity until they reform. A tight four or five formation box is deadly in game, even 88s, especially if they have a second gunner. Most will tend to fly full throttle though and/or inadvertently enter rudder inputs when in their fighting positions, this breaks integrity. The Luftwaffe pilots earned points towards Awards for separating a bomber from its formation, so boxes did help.