Mashiro, I don't think many of us around here
are normal... (I mean that in the best possible sense

)
The normal person in the Wii world is not necessarily an experienced gamer, nor is he/she someone who necessarily played the first Prime games. I believe this choice in difficulties was based on the Wii's userbase, which includes lots of new gamers (as in, new to Nintendo and/or new to games period).
Besides all that, there's the anecdotal evidence that I found Veteran in Prime 3 to be harder than Prime 2's default difficulty. And I'm not the only one who found Veteran to be pretty challenging (see KashogiStogi right above me). Should they have called Normal "Easy" instead? It's kind of a gray area, I think. Maybe Prime 2's default difficulty fell somewhere between Prime 3's "Normal" and "Veteran." That would seem to be my opinion, so I think what they've done is fine.
So, maybe Normal's too easy for you. But are you a veteran of the franchise? Maybe you should have chosen, I don't know,
Veteran, then.

The last thing we want to do is scare off someone who may be trying this kind of game out for the first time.
You know, really, WE'RE ARGUING OVER A STUPID WORD. "Normal" is the lowest on the difficulty scale. We should all understand that, as gamers, if we're looking for a challenge, we should just start out on Veteran.