Bad marketing, poor release window. I mentioned the game on Reddit once to some guy who knew about Dragon Quest he said "Wait there's a new Dragon Quest Game? I had no Idea". So, yeah basically because Square Enix didn't bother to promote it.
But I have heard it has sold decently in the west. The Steam Version did about 200k and the PS4 version was around 700k. Not bad for a niche JRPG that released around the same week as Spider-Man.







