Why do anime studios and producers discontinue making an anime? I've seen many series that just get discontinued, even popular ones. I'm talking about manga and light novel adaptations. Even though a lot of the story still remains left, and the first season gets critical acclaim. Some examples are Kaichō wa Maid-sama! and Baka and Test. Why do so many series stop after season one?
Most anime series are produced to promote the source material (manga, light novel, etc.). Thus for the producers its more important if the sales of the source material were boosted by the anime adaption. So even if an anime is quite popular - it should be noted that even quite successful anime only sell between 3000 and less then 10000 (more than that is rare is considered a very successful anime) discs per volume - there is often no point in producing another season if the sales of the source material increased sufficiently.