"A clarification of my earlier comment (since I realized I didn't word it as clearly as I had intended): Why do some cryptids from very reclusive/rural-oriented and/or endangered species (such Waheela/Gorgons/etc) choose to live in cities, as opposed to others of their species? Herd immunity (so to speak)? Cultural reasons? Genuinely curious here. (As to how Istas got involved with the Goth and/or Lolita subculture(s) )"
Well, first off, I'm not going to tell you how Istas got involved with the Goth and/or Lolita subcultures. If you look at the original post (which I'd like you all to do, since I need to do six more of these Q&A posts before the book comes out), you'll see the bit where I said "no spoilers." That applies to "how did character X wind up in situation Y" questions, since hey, I may want to write that someday. You'll like it better if I'm allowed to think about it longer, I promise.
Which brings me to the core question of "why do some cryptids who aren't considered specifically urban, like bogeymen (who hate living in the country), sometimes choose to live in cities?" Well!
First off, we have to remember that sapient cryptids, while not human, are still people, and every person is different. Istas is a serious social butterfly, for a waheela. Ryan is considered a little stand-offish, for a tanuki. Sarah is remarkably pleasant and non-destructive, for a cuckoo. And so on, and so on. You can make blanket statements about a species, like "waheela are generally territorial" and "tanuki generally live in family groups," but those will never be universal, any more than "humans are often suspicious and aggressive" applies to every single member of the human race. For someone like Istas, who actually likes things like fashion, cooked food, shoes, and having conversations with people she's not about to eat, living in the frozen Canadian tundra is just this side of hell. For a normal waheela, living in Manhattan would be just as bad.
Secondly, we have to remember that cities offer some opportunities that country living just doesn't, especially now that the world doesn't really believe in barter economies. If you belong to a species that can "pass" for human during part or all of your life, spending a few years in Orlando working at Disney World and sending money home to the rest of the family is just the sensible, responsible thing to do. Think of it as the cryptid equivalent of the popular interpretation of the Amish rumspringa: go to the city, live and work among the humans, figure out how dangerous and frightening they are, come home where no one's going to skin you and wear you as a fashionable coat.
It's surprisingly easy to be reclusive in the big city. In a small town where everybody knows your name and notices if you don't show up to check your PO Box on Wednesday afternoon, you're going to have a lot of trouble explaining where you went for those two months when you were hibernating. In San Francisco or Chicago, as long as your bills are paid, you can probably get away with it. Also, just like some humans don't like people but do like tigers/alligators/gorillas/whatever, some cryptids don't like their own species, but do like humans, regarding us as adorable and bizarre at the same time, and hence enjoy spending time with us, while still considering themselves "isolated" and "alone."
Finally...where else are they supposed to go? It's increasingly hard to live in a little house in the middle of a deep, dark forest without worrying that you're going to have a Wreck-It Ralph eminent domain situation on your hands. Much like most humans can't imagine going back to living with outhouses and no electricity and shoes only on special occasions, most sapient cryptids aren't overly excited by the "go live in a cave already" concept. There are rural cryptids, and cryptids who survive quite happily in places that humans still regard as uninhabitable, but for all the ones who evolved and adapted to climates similar to the humans around them, it's cities or suckage. So they choose cities. It's not their favorite option; thanks to us, it's the one that they have.