Well, I think Nintendo feels that not controlling the region of titles probably makes the system more vulnerable for... things. I don't know! I do know that Nintendo likes control, and not being able to specifically control what region titles release where is probably something they'd prefer to avoid.
The problem with importing for most people is simply the language barrier though. Even if they WANT to import, most never will because it's almost always pointless to import games you won't understand. I know there are games which use far less dialogue than others, but the headache of trying to figure out what means what would just be more investment than many would care to bother for. I guess for the few games that only come out in Europe and not the US, or vice versa, it might be a boon... but again, so few people would ever utilize it that Nintendo probably doesn't give a shit about them. Nintendo never was one to care about what the hardcore wants, in their post-GCN era.
The only game I ever was frothing at the mouth to import was Mother 3 (and the Mother 3 GBA), and I only did that because I knew we were getting that translation patch...