Considering the setting, I wouldn't be surprised if that shell was specifically chosen BECAUSE it looks primitive. Sorta the order of the day, innit? Besides, it's what's inside that counts.
The whole point of Aria is homely atmosphere and comfort. I mean, people still ride Gondolas - and they're not not powered by fusion or even solar energy. Unwieldy attempts at super-advanced and alien computer designs wouldn't have enhanced the show.
