According to the press, not a single member of Congress carries a gun in D.C (not meaning the Hill). Can someone explain why this is if they can easily get a CCW as politicians?
First, if a congressman has a CCW in another state, it doesn't work in DC because DC doesn't offer reciprocity with any state. It is likely that congressmen rely on their personal security detail and consider that threats in Washington DC are minimal compared to their home states because of the nature of the circles they travel while there. This will probably change.
Second, even though congressmen could get a DC CCW easier than you or I, they still probably didn't want to go through the hassle of it. They will now, probably.
National map on CCW laws and reciprocity.
https://www.usacarry.com/concealed_carry_permit_reciprocity_maps.html
You can click on the state of interest and see how reciprocity works. For example, I have a Florida resident CCW. You will see that there are a few states that do not recognize my license - not that I would ever want to go to any of those states (if you click you will see what I mean).