I've never been sold on the worth of having random celebrities doing voice work in animated movies, at least for every main character, a big star who has is well cast can for sure help the box office but most aren't that. Let's take Shrek, Mike Myers and Eddie Murphy for sure helped the movie, but Cameron Diaz I would be shocked if she justified her paycheck. Most of these celebrity voice roles aren't because they fit the role, but because they are the most famous person they can afford for the role. See that why with a lot of cheap movies they market the fact they got Rob Schneider.
Rise of the Guardians, that movie had a cast of Chris Pine, Alec Baldwin, Jude Law, Isla Fisher, and Hugh Jackman, it lost $90 million, Meanwhile Coco a Pixar movie which didn't have any well know celebrities was a huge hit. If the audience like the look of the movie, an all-star voice cast doesn't matter.
The craziest ones are Alvin and the Chipmunks movies, they use sped-up voices, so why does matter who voices them, well to the studio it did, with a voice cast of actors like Justin Long, Christina Applegate, Amy Poehler and Anna Faris, adding millions to the budgets they really didn't need to spend in the first place.
It's just mostly a waste of money, but Hollywood loves to waste money.