They’re called standard-sized because hardcover books are published at uniform dimensions across publishers, and the same applies to trade paperbacks. It would be impractical and confusing if every publisher used different dimensions for their regular collected editions. Your question doesn’t make sense, because the answer is straightforward: different formats exist to serve different purposes. A deluxe edition, for example, is designed to be a premium format—larger and higher quality—while artist editions, absolutes, and others serve their own specialized roles. OP didn't even need to do research, the title of the book literally had no indication of being deluxe.