I would, but:
* I really like meat and I can eat a lot in one sitting. Especially, if there is nothing else to fill my stomach. So I'll end up with a calorie bomb at each meal.
* Depending on a person's size and build, there is just so much protein that can be absorbed by the body and used for muscle repair, the excess would most likely be converted to glucose via glycogenesis. I have read that if this process is occurring regularly, it could be very taxing on the body.
* I like my veggies and fruit too much.
* I don't want to miss out on good nutrients.
With that being said, if all meat diet is what works for some people, more power to them.