There are many things that don't need a movie
Another reason is that Fruits Basket has loads of characters. There are 14 cursed people- all 12 of the original Chinese zodiac, Kyo, the cat, and Akito, the god. The interactions between these loads of characters is why Fruits Basket is popular. It's not because of people bumping into girls and turning into animals! Nor is it because of Hollywood style romance. We see friendship grow first, and then, tenderness, and then, love. The emotional weight of that such as it is can't really be expressed in a love montage.
There are other issues, such as the fact that the Sohma compound is very well...Japanese. I can imagine Shigure's house in America, and maybe the school, but not the compound. I of course wonder why every movie has to be set in America or fantasyland. There are so many great stories in America- women's stories, black people's stories, Arab people's stories, Latin@ stories, Native American stories- that aren't being told in film. Why go to some other country and butcher their comic book by Americanizing them when we have so many great ideas here?
More people reacting in pure horror