The idea is to be able to use it without a network access, such as looking for unstructured URLs in text (e.g. "get a discount code at example.com/hn-reader"), formatting a URL in a browser bar (e.g. put the non-eDLD+1 in bold, or at least show the site name properly and not abbreviate all UK sites to "co.uk") or managing the cookie name properly (again, so everyone in co.uk doesn't share the same cookie).
Presumption is that the eTLDs are a tiny fraction (by orders of magnitude) from the domains registered under them so this db doesn't have to get too large.
I am not sure how to manage these strings automatically without them being spammed. They aren't all under the control of the TLD administrators (com.au is but cheapo-shop-hosting.com.au is not).
Can anyone explain why something like this wasn't implemented in the first place via DNS TXT records or tied to SSL somehow?