With errata and FAQ's coming out soon after Codex releases (except Eldar) would you buy a reprint that included all of the updates?
Some other companies do this. While I don't think GW would, I for one would drop another $50 for the same codex, but with the included errata, FAQ, and typos fixed.
This would also be an incentive to sell the digital versions and they do get updated for free.