US Government bodies do a lot of public outreach, many have twitter/social media accounts as part of that effort. There are many reasons for this- the aforementioned help at budget time, Government officials geniunely want to be seen and celebrated as doing a good job, and a surprising amount of belief that the American people should see what "their" government is doing.

The interplay with that last point (belief in transparency) interacts with institutional secrecy in weird and hillarious ways. I remember one project I worked on was shrouded in secracy to the individual teams working on it until a news program showed up and talked to the public affairs office and senior leadership. After watching the broadcast, we all of sudden understood what the heck it was we were working on!

I imagine some employee needed to show they were doing something so they got the idea of making a twitter account for their department. Or it benefits them if they can add a bullet point on their resume such as “managed social media acccount”.

Even better if they can increase their budget and headcount and hire someone to post things. But then they need work to do, so you tell the person to make posts bragging about busts a government agency is making.

Positive media exposure can be used as evidence of effectiveness in annual budget request battles, as it is a pseudo-metric that government leaders find impressive.