I know ESA releases their images under a non-commercial use only license, but there have been attempts to try and open that licensing up a bit more to something more akin to the standard CC-by-SA type license.

"Standard" is overrated. It's "standard" in our little world of free content providers. :-) Never forget that most people in the real world have never heard of content "licenses".

Having been personally involved in the attempts that you mention, I can tell you that the issue is really complex. Any attempt at comparing ESA and NASA completely misses the difference between legal systems and operating environments.

trying to milk every last drop of money from content produced by salaried employees of these governments

There's something to that but it's not the main issue in the case of ESA.