The city population grows by 80% every day, more than any other American city. Federal government offices close in DC because alot of workers are come into DC from all over Virginia, Maryland, Pennsylvania and even West Virginia and the snow removal in all of those areas is variable.

Plus winter temperatures in this area are often right at the line between snow and rain so every storm is a crapshoot as to what kind of preparation is really necessary.

Teleworking is becoming alot more common so the offices closing really isn't as big a deal as it once was.