Music these days is listened to in cars, subways and sidewalks. All with a steady ambient noise. If you listened to the HD track version of DT in those environments, you'd not be able to hear half of the music because it wouldn't be able to cut through the ambient noise.
So, they compress the shit out of the music. That way you will hear every aspect of the music in those environments.
I agree with you in general. However, I just listened to the HD Tracks version of DT12 in the car on the way to work today. It was still much better than the CD version, mainly because there's no crackle from clipping of guitar and other parts in various songs. The "HD" version was worthwhile for that reason alone. Yeah, I had to turn up the volume a bit more, but it still sounded great in that environment.
Also totally agree with those who say that the improvement has nothing to do with bit depth or sampling rate (what makes these technically "HD"), but everything to do with the improved master. 'Tis a shame this master wasn't used for the CD.
If I'd known about this version ahead of time, I might have bought it in lieu of the physical CD - I'd never buy a CD again if download versions had at least lossless CD quality instead of lossy compression (don't care about "HD" but I'll take it if available). I'm no audiophile, and probably couldn't tell the difference between 256kbps MP3 and CD (let alone HD), but that extra peace of mind with "lossless" is nice.
Every CD I buy goes into the computer once to rip, and then into the closet, never to be seen again.
The one nice thing about the physical version, though, was the 5.1 mix on the deluxe version - which also sounded PHENOMENAL. Now if HD Tracks would offer multichannel downloads, too, that'd be perfect...