Here is Monster Hunter producer Ryozo Tsujimoto explanation for why the 3DS version of Monster Hunter 3 Ultimate doesn’t online multiplayer:
“To put it frankly, when we were developing the game we were looking into it but there were some places we were unsure about. We didn’t have the correct techniques to get it to work. We decided we probably shouldn’t release something that didn’t work well. We didn’t want to lower the quality of the game.”
Sigh… We get the game but not the whole game. Why must you torture us Capcom!!! Anyways… At least the Wii U version will have it.