But again, I'm not saying that there are no benefits to TLS, just that a blanket policy requiring TLS for _every_ government web service is a bad idea. One that prefers TLS or a best-effort-to-support TLS policy would make more sense.
Look at the history a bit. InCommon's use of insecure hashes required that all clients re-issue their certificates in order to avoid browser warnings. At the University level that was impractical to do quickly. At a federal government level? That's a whole different beast.
And look at heartbleed. How long did it take the federal government to make all resources secure again? Is it actually a completed project?
There's operational overhead to consider. There's the fact that MITM for http is minimally different than https. There's the plain and simple fact that a lot of data simply does not need to be secure. And there's the fact that there are already existing problems with making data available to the public at large.
If you want to provide confidence in government data, you could say that all certificates used by government resources are secured by X,Y, and Z certificate authorities and that would be a legitimate benefit.