In a news-article on Siliconera, head of Nintendo, Satoru Iwata, talked about the stronger focus on online-features regarding the upcoming Nintendo 3DS-handheld. He called it a bitter learning experience to get people online with Wii and Nintendo DS. It is still in the dark if 3DS will feature any (strongly) improved online-capabilities, since Iwata focuses talk on 3DS´s wlan-features, called SpotPass and Tag-Mode, that exist to use set up hotspots to connect to the internet. Something that might work for Japan, hardly for the USA, and definitely not for Europe.
However, people are criticizing Nintendo´s online approach as whole for a long time now. It has to be said that Nintendo most likely doesn´t have “crappy online” just for fun. Biggest evidence of that is the warning-screen that pops up every time you start your Wii or NDS. Not using any different technology in terms of “being dangerous”, it is only Nintendo that “has to” use these warnings. That, in combination with the emphasis on friends code, should make clear that Nintendo actually fully addresses to any kind of danger that could come from using their systems. It might be a hassle for adult gamers to be have no choice of being protected by these decisions, but it can´t be argued that it works. Anyone who has ever used Xbox Live and voice-chat knows what a more open system brings alongside.
The other reason is that Nintendo is Nintendo. Instead of giving gamers the obvious, they´re looking for something unique. There was an interview with Shigeru Miyamoto many years ago where he was asked about online-gaming (I think it was before the GameCube´s launch), and his answer was basically: If we cannot create new kinds of games by using the internet, we have no interest in that. We don´t want to simply put our existing games online without any innovations.” So, while online-multiplayer is vital to a lot of enthusiast gamers, it surely isn´t anything special or unique. I´ve wondered myself what new game-genres could be made, besides online-multiplayer and mmorpgs. Seems that Nintendo hasn´t come up with an answer, either, yet.