Much of the conference standards of E3 are tradition.
E3 was great for 2005 when there was no viral social networking, convenient internet stream. Journalists had to go to events write articles and post screen shots.
Today, it's simple to just post the footage online and watch it disseminate like wildfire. Nintendo can straight cut out the middleman.
E3 is good for actual gameplay where journalists can try a game hands-on, but aside from that conferences aren't neccesary?