Board Thread:Questions and Answers/@comment-28194879-20160519003219/@comment-5774380-20160519050927

The first reason would be because Wit Studio has very few employees (34, actually) and they are unable to produce an uninterrupted series with such a short staff list (it is taking them forever to produce only 25 episodes...).

Second reason would be, because that's how it is. There are animes that are aired uninterruptedly and animes that are aired in seasons, and this is not necessarily caused by the manga (Shokugeki no Soma, for example, is a weekly manga and yet the anime adaptation is released in seasons). It is simply because that's how they chose it to be.

And I should note again that an uninterrupted airing carries the problem of the fillers. Since the story in the anime flows much faster than in the manga, the anime needs to insert considerable amounts of filler content to allow the manga keep up the pace. Sometimes they even make up entire filler arcs for this reason, which not only don't contribute to the story, but potentially create plot holes.

So in conclusion, monthly mangas and seasonal animes win again. ;)