That's not as good an example as you might think. The Rural Electrification Administration's mission to bring electricity to rural America was essentially finished by the early 1970s . After that, it continued along for another two decades in the time honored tradition of a bureaucracy trying to justify its existance. Before the REA was finally disbanded in 1994, I've read that one of it's last projects was providing cable TV service to Micronesia. That's a far cry from the original mission. Of course, they really just changed the name to the Rural Utilities Service and keep chugging along.

Many bureaucracies continue to exist long after their reason for existance has passed. In fact, as Parkinson's Law shows, they often expand even as their need diminishes.

The same thing happens sometimes with charities. For example, the March of Dimes was established to fight polio. They did wonderful work and ultimately succeeded with the polio vaccines. Rather than declaring victory and closing shop, they changed their mission to fighting birth defects. Certainly, that's a noble cause (and a much less likely to win cause than a specific disease), but it's hardly their original mission.