From what I saw looking around most people think it got cancelled (the publishers) but it could be the author himself . . . or, and this is a longshot here,
But, I really doubt that it would happen that way. It was most-likely the series was cancelled for whatever reason.
But, to contradict my own point, usually when a series is cancelled the author/s are told that they have around 4 more chapters and the way the author was leading it so far has been a lot longer than 4 chapters so who knows but I think I'm going with something like the spoiler above. Either way it was a good manga and I'll (probably) enjoy the ending