Deaf people can't read the lips of people speaking a language they don't know. If you dub a movie into their language it does no good. If you subtitle it then they can read the words.

Don't just worry about preserving the cultural nuances.

Make the film accessible to the most people you can.

Of course, if you are blind then subtitles won't help you at all, but you can still listen to a dubbed film. Thanks to Starke7764 for pointing that out to me. I suppose this demonstrates how well produced DVDs are helping to make films more accessible to all by including various soundtracks and optional subtitles.