If you convert the time of the Japanese server maintenance, it lasts from 6am to 8am in Japan. NA server maintenance lands anywhere from 4pm, 5pm, or 6pm until 6pm, 7pm, 8pm, or 9pm. It's pretty blatantly inconsiderate of them and they are most certainly taking the servers down during NA prime time, however, they manage to schedule Japanese server maintenance during low demand hours. Now, if you convert an average work day (8am-5pm or so) in Japan to EST, you'll see that it overlays 7pm until 3am in the states. So, it would be incredibly simple to schedule server maintenance at the end of a work day, and line it up with 1am EST. Now, of course the people on the west coast would still be dissatisfied, but you'd pacify pretty much half of US.

The question is, with so many North American subscribers, why wouldn't you?