Why is Urban Goth Literature considered Gothic?What is it about the "urban" setting that makes it Gothic? What is urban Gothic Literature? How...

I think you're already on your way to answering your own question, but I'll take my shot at helping to explain the concept.

Urban gothic isn't a new term, as far as I know, and was used to describe some late nineteenth-century novels in which, for examples, young women who came to a big city for work ended up imprisoned by an evil man in some beautiful-appearing home. As I understand the term, gothic often refers to decay, decline, confinement, fear, irrationality, and a number of other dark elements. These elements can be found in cities at least as easily as in the countryside.

When I think of gothic literature, my first thought is of Edgar Allan Poe's short story "The Fall of the House of Usher." The house -- with its vacant windows and cracked foundation -- is out in the country. The abandoned warehouses that you mention in your question seem very much like the urban equivalent of that decaying estate.

When it comes to psychology and the gothic, my first thought is of Sigmund Freud, who famously attempted to explore the dark, irrational elements in the human mind. Freud's concept of "the return of the repressed" seems to me to be clearly manifested in gothic literature of all sorts: insanity takes over characters despite their struggles to remain sane, people you though were dead smash their way out of crypts, etc.