I think the biggest problem is that (at least it used to be that way) icons can only be turned off by players themselves.
Even if everybody follows a rule to leave them off, it opens the door to accusations. Whines have been recorded for less
In one of the eastern front Scenarios (or Snapshots based on it) icons were off. It was cool because you had to be careful and properly id who you are shooting (friendly fire became more of an issue) but the reason icons are in AH are still valid - the inferior screen resolution compared to RL.