Alot of anime's finish up quickly and somthing that I have found in alot is that they start making the anime while the manga is still going and decide to give it a fake ending to satisfy the fans. For example they made Negima and anime but the manga is still being written to this day, even though Fruits Basket is finished that is the only thing I can really think of.
It is sad when an anime is stopped especilly if the manga keeps going but in a way sometimes it's good. I liked the ending of the Fruits Basket anime and probobly wouldn't have enjoyed it if it kept going because of the depression and Hatsaharu.