In every city I've been to, the majority of people you meet are locals. People who are very familiar (bored) with their city. People who think everyone in the world is familiar with their local music scene or local slang, or locally famous spots. So when you go to these cities, it takes about a year to get familiar with all of this, and even after that year you are still an outsider compared to the huge numbers of people born and raised there.
D.C. is different. The vast majority of young professionals (and older professionals) in the city are not from the area. A lot of the 'locals' are not actually from D.C., but from neighboring cities in Maryland or Virginia. No one is shocked when you say you're from across the country and moved 2 weeks ago--they're from Israel, or Ohio or Texas or Argentina. Rather than being one of the few outsiders in a city, you are among the majority. It also gives it a certain character, as many people chose to live in this city. Politics lives in D.C.-- it is no longer just a tired argument far away on a television; people moved their lives cross-country to work in politics, guests on news shows are now people with coworkers that you know, and you pass by their workplace in your morning commute.