Board Thread:Questions and Answers/@comment-80.132.99.68-20150329114408/@comment-918376-20150930201849

No, because volumes 1-6 were already published by the time Season 1 was produced. Volumes 7 and 8 were published during S1's run, and then volume 9 published around the time S2 began airing. DEEN already had material to work off of when they began production, but then they surpassed the original material.

Also, two different studios worked on the anime (S1 was Satelight, S2 was DEEN), which shortened the amount of time between seasons. They don't have that liberty for Season 3, since Mamare (the author) stated himself that he rushed himself to get volume 10's material to the anime production team. And he's just published the light novel form, some five-six months after the anime aired.