*"I've never heard of that before...  "

*Actually, I've heard JIm Carey, Robin Wilams(sp) and a couple others talk about that as the way they do it.

Imagine a fist-a-cuffs punch. (as an example)
Punch,,,, thud

There is a natural timeing to the sequance that would sound WAY off if it was to fast or to slow.
So, to have a working sound script it would be far far easier to match then to try and match/stretch/compress the sound to fit an allready existing animation.