Cities change things, that's just the way it is. Old ways fall away and new ways rise up, usually while the past and the old ways of doing things lose their original meaning and become idolised without a proper context. Urban Fantasy is more or less based on this idea, along with the obvious 'things are not what they seem' angle that's common to the genre. Monsters, which in horror would have single-minded and rather shallow motives (kill humans, possess humans, feed off humans etc, etc) suddenly are part of communities and have to deal with issues like politics, or love... Or paying rent on a space to live, Other issues become prevalent as well, can a werewolf really risk hunting and killing prey inside a city's borders, can vampires rely on nightclubs for their blood when there's a shortage of virgins to go around? They change and new priorities arise as they interact with other communities and with protagonists (who may or may not be monsters themselves, ...