This was raised by Adrian Cunningham in his most recent blog entry. Link rot is a universal problem but happens regularly as government departments change their names and acronyms every few years.
Persistent URL resolver services are well established in the scientific community but rely on the goodwill of a few key institutions to provide the resolver services.
To guard against link rot and to support semweb activities it makes sense for the government to have its own resolver. PURL server source code is open source so the cost is minimal.