probably because they've tasked FF Tactics' composer to do the score, ff12's music sounds so far like this guy's rather upbeat military march-themed songs. I thought Tactics' music was fabulous, and suits ff12's setting (so far as i've seen) but do you think Nobuo Uematsu's legendary electro/melancholic style could have also worked? hs is doing the main theme of ff12 after all.

check out some music, courtesy of ffxii.net

http://www.ffxii.net/?nav=media/music