I mean, there are a number of reasons...
1. Since NISA will be localizing some of Imageepoch's new games, why not the old ones that never got localized as well?
2. The first and second games were released by Atlus, but I'm pretty sure they don't plan to localize this... If they did, they'd have announced it by now. I'm sure anyone that's played the first two in English would like to see some closure.
3. From what I've heard, it's a lot better than the first two, so I see no reason as to why it hasn't been localized (unless there are some "issues" that I haven't heard about)