I thought that was strange also. The music is pretty thin and dated, and there's not much to it. Not something I would want to hear again.
Sometimes the Academy gets on the "nominate them for everything" bandwagon, and since "Heaven Can Wait" got a large amount of nominations, that was one of them. Grusin's music doesn't even compare to heft and majesty of "Superman" that year (which also lost.)
I think that the soundrack is very suitable for the film, I think it fits perfectly. It may sound dated but I guess it was done intentionally because it sounded dated even when the film was released just like the Farnsworth life style (what about that canon and Mr. Farnsworth clothes and hats?), the soundrack seems kind of sarcastic and it is one of the reasons I like this movie.
I just caught this on tv and haven't seen it for years and I was struck by how similar a lot of the music in Arthur was. It's really astonishing. I'd have to listen to them side by side but that bouncy saxophone music was virtually identical.
i'm a fan.