I think there's a difference between hip-hop music and rock music, though. It's less important for hip-hop to have the dynamic range because the majority of its emotional expressiveness comes from the words, rhythm, the way they interact and the changes thereof. This is why having a great beats is so important and so good producers attract a lot of attention (e.g. Neptunes, Dre). Volume is not as important a factor. You really only need two levels of dynamics: one for the verses, one for the chorus/hook.

On the other hand, I think changes in volume are more important for expressiveness in rock music, for instance, in an unexpected bridge just when you feel the song is about to end. Now, most bands these days seem to compensate by having simpler dynamics, but I think it would be nice for them to have more options.

Also, wouldn't it be easier to have a good mix now that we can do most of these things on the computer instead of having to manually twiddle knobs and overdub live?