Being "sensitized" to violence, death, war, etc. is a relatively new thing in human society, anyway. Historically, children have been surrounded by death, violence, etc. Not too long ago, it was commonplace for most children to never survive to adulthood, with nearly half dying before they even turned 5 or 6. Most men were destined to die in war, many women were destined to die in childbirth. The idea that death is kept so distant from our society is something that developed in a post-industrialized world.
Children have played war games for centuries as well, so violent video games aren't really a new concept - children have always played violent games. So I don't think video games are allowed because it helps military recruitment later on. I think it's just what people do - prior to video games, there were other games parents thought of as "too violent", etc.