Sheer number of titles to be localized is to blame.
In an interview with Official Nintendo Magazine (UK), Nintendo of Europe representative Laurent Fischer has accounted for the late arrival of Super Smash Bros. Brawl to the European market by stressing the size of the overall localization workload in the region.
According to Fischer, the European localization team behind Brawl is part of the "same pool of teams" responsible for localizing all of the numerous other titles being released by Nintendo in the region. These teams must translate games into multiple languages: a process that applies not only to text, but to voice samples as well, creating a significant amount of work to be done in the case of Brawl.
In addition to the impact of translation efforts, Fischer also cited production issues as contributing to Brawl's European delay. Hundreds of first party and third party games are on the global production line, and there is also the possibility that extensive localization may create bugs and other issues that must be resolved before pushing the product out the door.
Finally, Fischer apologized for the wait and stated that Nintendo of Europe is taking strides to improve the situation in the future.
"We know that we are still not reaching the expectations of all the people, but we're really doing our best to resolve this."