Outside of maybe Cass, Jason has been the child who would have regarded Bruce as his parental figure the most. Dick had the Graysons, Tim had the Drakes, Jason had an absent father and a mother who betrayed him.
Dick didn't have the Graysons. He was raised by Bruce. Of course he regards him as a parental figure. They all relate to him as a father in different ways. Dick's just the oldest so teh one who's made the transition to adult parent/child relationship.