I can't see why that would be advantageous.
In the library I want to see the images as I've edited(corrected) them, not raw.
I can't speak for John, but ... several other apps do or have done this and it is invaluable when performing first cull on large imports ... not for viewing past works. Then, of course we do want the Lr generated previews reflecting the results of the efforts performed. It would be nice to turn off the process at the beginning of the process.
Waiting needlessly for Lightroom to build previews when the embedded previews are more than adequate for checking focus accuracy, basic tonal evaluation and composition.
Anyone who has used Photo Mechanic or Aperture where you could use this procedure, would see the value of increased speed for the initial import for meeting stringent deadlines for publication when working with larger volumes of images for sports, news and event coverage.