Many of these government repos are having problems because they're stuck in an old bureaucratic process. Their official process involves a static website with a list of software that has passed a review and release process. A developer will submit a bit of software for release and some other department will publish it on the website (after approval by everyone and their brother). The developer will need to perform this process for each release.
This doesn't translate well to Github. The developer will submit their software for review and another department will post it to Github. They're using Github like the static website that they used before -- there's nothing in the process that keeps the developer tied into the project once it's released. The developer may not actually have permission to their software repos because some process forces them to only release it through another department (they're definitely complaining about this, trust me). This completely breaks pull requests and may be the reason for the lack of response.
It would help the developer if they could point to Github and say: "Look at all of those pull requests we've been ignoring! Our process is broken! We must fix it!".
If external developers feel that the project is dead, or they're being ignored, pull requests will not be made. However, if there are no pull requests, it's tough for the developer to make an argument to change policy. The circle here needs to be broken.
If you've ever worked in government, you'll understand how difficult it would be to get this process updated. It will be updated eventually, but probably not in the near future -- especially for agencies that don't have a larger group of developers.
Having said that, not all government repos ignore pull requests. I manage a few "government repos" and try my best to respond/merge within 24 hours (most of my responses are under an hour -- even on weekends). It helps that we have a ton of developers who constantly push to keep things open. Even then, it was only in the past few weeks that we finally took down our static list-of-software website.
TL;DR, please don't give up on submitting pull requests. It might even help out the developer if you complain a bit to the folks responsible for "review and release" (which will probably consist of multiple departments).