I don`t think that`s the reason. People know that no matter how good this E3 ND will be, it will be because it`s a replacement to the usual E3 conference.
The reason is that NDs have more audience than last E3s.

To be honest i don`t believe that ND is only for fans, when everyone knows about them and they have even bigger audiences than E3.

I do hope that they take advantage of not doing a live event and add some digital animations with Nintendo characters. And stuff like that!

Good Read

Well Nintendo said that all the Media will be able to play with their games in a closed event. This means they won't be waiting in long lines for only 2 mins of play at a kiosk before they are shooed away to play at some other games kiosk. The media can take their time and fully enjoy the demos and make detailed reports on the fun factor. People saying that E3 is streamed on other outlets that's true but they are put on video game channels the same channels only gamers watch; the gamers who would already know about Nintendo through game websites and magazines.

I think there is some relevancy to this. Nintendo has developed NDs as their communication tool. They don't want to break from that. NDs are like Nintendo Power used to be. They will have their e3 conferences but we at home will get the info through DC, probably a special e3DC.