In boxing, we enjoy watching two men fist-fight until one of them no longer stands. Many pay a premium to watch the Ultimate Fighting Championships, a no-holds barred competition, where the winner is determined by either knockout or submission. The participants engage in bloody, bone breaking, full contact combat, with no protective equipment. The fact that there have been nearly seven of these competitions speaks to its growing popularity and appeal to our deeper desires. Finally, the primary example of our pleasure in violence is professional wrestling.
Television is a business.
They earn their paychecks on advertisement revenue. Advertisers want to reach as large an audience as possible. Therefore, they shell out the big bucks to the station that can achieve that goal for them. Thus, television stations are obligated to their shareholders to maximize their profits. They do not air violence because they want to.