Why did the Strawberry Panic manga end?


I picked the so-called 'complete collection' of Strawberry Panic at a
convention. Upon reading it however, I found the story wasn't actually
complete (stops just as the 'faceless devil' event is announced) and closes
with an "..end?" even though nearly no plot points are resolved and many
events are about happen

I've read the light novels, and there's a good chunk of story left. Why was
the series stopped so suddenly?

![enter image description here](https://i.stack.imgur.com/Fom3g.jpg)




Generally, a manga/anime doesn't have to complete the story set out by the
original material it was adapted from. Some examples are _Accel World_ ,
_Bleach_ , and _Bodacious Space Pirates_.

Some reasons are obvious, like key changes in the plot making it impossible to
follow the original plotline set out in the source, while other times it's not
so obvious such as events involving members of the production team, such as
work disagreements, licensing problems, or people getting sick for an extended
period of time.

This isn't just for adapted works as these problems can affect the source
material: _Kaze no Stigma_ 's light novel has been left incomplete due to the
[author dying](http://en.wikipedia.org/wiki/Kaze_no_stigma#Light_novel).

