Most D&D adventures take place in the wild and untamed areas of the world. After all, that’s where the monsters live. If your objective is to destroy powerful monsters and loot their treasure hoard, then you can expect to travel to far off places. After all, how many ancient red dragons have you ever heard of that live comfortably in a two-story townhouse in the merchant’s district of your local town?
Urban settings in D&D tend to be the place the PCs go after the adventuring is done. It’s difficult to adventure in the city since fighting in the streets is generally frowned upon in most civilized urban areas. If you’re used to killing everything you fight, then having to pull punches and not execute the local authorities when they come to break up a bar brawl might be a reluctant change of pace for many players and their PCs. Who would ever want to play a long-term, city-based camping? That depends on what type of PC you’ve got.