Part of it is that at 48fps, these movies won't visually match the LOTR films. Not to mention the 3D, which a lot of people are tired of. I wanted a somewhat consistent look to make the series feel more cohesive. Leave the visual experiments for a new project.
I admit that I'm a traditionalist in a lot of things, and 24fps is the classic movie look. I also don't know how 48fps will look, so maybe I'll be pleasantly surprised, but I just hope it doesn't take on a soap opera effect. The more it looks like reality, the more it might look like a bunch of goofballs in silly costumes and wigs running around because we're so used to having movies appear a certain way and the illusion could be broken.