Because Tom Brady is 35 years old. Simple as that. While he certainly isn't ancient, he's getting up there and father time catches up with everyone. Wear and tear comes into effect. The more he drops back, the more chance there is for injury. It did not make any sense at all when we were stomping teams last year, and Bill O'Brien still had Brady slinging it when we had a great OLine and just drafted 2 Running Backs. To be honest, I think O'Brien just wanted to inflate his numbers so that he'd have a better chance at getting a Head Coaching job himself. A greedy mentality. Pounding the rock may allow Brady to extend his career an extra year or two.