These categories, while completely separate, can work together. My friend travels for his career, and along the way he often takes a lot of black and white photographs. When he travels, he is able to capture images of people, their lives, and their culture. These different elements mix well for him. He also has a studio and shoots studio imagery to generate income and offset his mix of skills.
Some photographers can hone their interests into a single specialized skill such as food photography. If there is one formula that keeps you happy, provides you with ongoing creative and visual challenges, and brings you a comfortable income, then that formula is the perfect photographic "specialty" for you. My studio is unique and leans toward the other end of the spectrum (fashion, advertising and modeling) it specializes in many categories.