While reading though the forums on aikiweb, I came across this link. There, the author writes about why we train with weapons in Aikido (although, in my opinion, the answer applies to many martial arts).
I highly recommend checking it out. I think it’s a well-written response to a common and excellent question. What I like most about the answer (sorry, I’m about to spoil it a bit for you) is the re-phrasing of the question: “Why do we practice with weapons?” to “What do learn from practicing with weapons that we do not learn anywhere else?”
What I enjoy about this re-phrasing is that, quite often, I find myself thinking: “Why?” Why do we move one way, and not another? Why do wear hakama, instead of sweats? Why do we bow? But the question “Why?”, as the essay I am linking to illustrates, may not be enough. The truth is, almost any action, if done with deep conviction and intention, can provide a level of self-understanding. When I expand the question to “What does this particular action teach us, that another action cannot?” I have to think harder about the answer.
AikiThoughts 
Aside from the fact that training with weapons remind us that the martial arts were originally the ways of killing, that link you provided brought up an interesting point: The concept of gaining victory before actually striking. This is all tied in to intent, visualization, perspective and other aspects of the martial arts that tend to get glossed over in some schools.