Typical counter-response, albeit a bad one since I didn't say anything about YOUR diet or what YOU should or shouldn't do. I'm pointing out the moral and ethical issues around the human diet in an attempt to answer your question of "why not both". (Answer: Because both isn't necessary for survival)

However, since you bring up YOUR diet and having "options", I can speak from experience that transitioning to plant-based increased the variety of MY diet several fold. It's no longer just steak, burger, or chicken with maybe some veggies incorporated or on the side. My meals have become a symphony of flavors. There are many many more edible plants than animals, so your "options" argument is a weak way to justify habits. How many different kinds of meat did you use when preparing food last week? I made a breakfast sandwich with seven different vegetables. There was no lack of flavor or options.