I''m not convinced realism is a good argument. As well as the various negatives that realism would bring (occasional gun jams, incremental crippling from damage, etc) there are things where realism could potentially assist the player - invisible walls round play areas, inability to fire in a direction other than where you''re looking, lack of kinaesthetic feedback, inability to "glance", inability to squirm through tight places, inability to converse freely (OK, some multiplayer games do let you voice chat freely)

At least a few of these unrealistic disadvantages appear to be inherent in current hardware limitations (roll on VR) or at least a consequence of the standard "single monitor" setup. Until there''s a way to overcome these, I think it''s inappropriate to add disadvantages to the player purely in the name or realism...