Living vicariously is the essence of being human. It's why we have language, and stories, and imagination, and all the wetware required to support these things. Dogs can't tell stories about other dogs in such a way that their canine audience is moved to weep or cheer. Whereas humans line up to hear stories about three-thousand-year-old semi-mythical events. Then they draw practical conclusions from those stories.
I don't see why it's so terrible that I'd rather watch, say, a deep-sea fisherman risk his life than try deep-sea fishing myself. We have no shortage of deep-sea fishermen -- in fact, what we have is a shortage of fish. And the same principle definitely applies to soldiers: Every real soldier who can be replaced by a Team Fortress player, or a History Channel viewer, represents a net win for humanity.