It’s only been out in America for more than a year or so..
There is also the 3DS retail version out now, so why would you care? The 3DS version doesn’t have a 2D-oldschool-look and (in my opinion) doesn’t look anywhere near as awesome as the original does, that’s why! When I heard that the 3D version was soon to be released I already knew that there was a DSi version and I tried downloading it, but it was nowhere to be found. Since I couldn’t find any reason for this I assumed it was either removed to keep people from getting that instead of the new, full retail edition or it wasn’t our in Europe. The latter, as I have found out today, is the case. Gladly, all hope is not lost, as Nicalis, the game’s publisher, has revealed on Twitter that they’re working on getting it released at some point. It was apparently rejected by Nintendo of Europe when it was originally submitted due to “some really minor crap with the manual”, which they are likely to have fixed.
Or you could just get the game on Steam for really cheap and play it like that.