Here's the thing. I do some work for a government department in the UK. They gave me a personal email address as part of my account but no one is supposed to use it because all the emails are supposed to be sent to an address that can be seen by everyone on my team. I am not unique in this, there are other people at my firm who never bother to open the email box the department gave them because its not relevant to their role. I can well imagine there are plenty of lower level people in those US departments who never bother with their personal email boxes.
ETA: Oh and I frequently send emails to people in those departments only to get back out of office emails or zero response because it was buried under a blizzard of other emails, all marked as priority.