Both acts are vehemently opposed to digital download sales and it appears they may have a point, since the lack of downloads hasn't seemed to deter sales for either.
While some say this was a brilliant move to keep fans from cherry-picking only their favorite songs, other would say that CD sales might've been even greater if these albums were available digitally.
It's also possible that Kid Rock and AC/DC's audience prefers CDs to digital downloads, something we've seen before from hard rock fans. Unfortunately there's no way to tell definitively if the addition of digital downloads would've helped these acts sales, but it hasn't affected the sales for #1 selling Lil Wayne or #2 selling Coldplay.
CD sales will never return to their heyday, but there does seem to be a place for them, at least in the near future. What could change the equation is if hardware manufacturers stop making DVD players in favor of cheaper flash memory units, which have no moving parts and are therefore a lot cheaper to manufacture. We'll see how close to reality these units really are at the upcoming Consumer Electronics Show in January.