Seeing as it wasn't released in Europe, came out years ago on the previous hardware, and even in the US was a late, niche release that might have been easily missed, I think there's plenty of 3DS JRPG fans who haven't played it. Not everyone imports games or has played portable RPGs for at least six years. RH and SJ are good picks for remasters, as incredibly niche games often ignored on release that, over time, have gradually been recognised as two of the best portable RPGs.Radiant Historia 3DS is nice and all, but considering every JRPG fan who had a DS probably played it already, methinks there is still plenty to whine about in terms of when there will be a sequel...
Also, people enter the hobby and some lapse all the time, I'll never understand the sentiment that 'everyone already played that 6/7 years ago', as if the gaming customer base was set as a specific group of people decades ago, with nobody entering or leaving the hobby. That's why GTA and Mario Kart keep selling years after release, and games aimed at kids sell, as a sizeable portion of new players pick them up.