[Kath]

Maybe they felt that only Frodo should feel the incredible pull of the Ring because we were going to focus on him throughout the film. The scene with Galadriel seemed to be more about telling us what the Ring could do in the hands of a more powerful person rather than the power of the Ring alone as in the book.

Also, we had already seen Gandalf refuse to take the Ring with reasons why so they may have thought that there was no need to explain it again.