With today's 3D targets getting smaller and smaller it's very easy to accidentally hit one of the pieces of metal in the legs. At one time, this wasn't a huge concern, but I have seen a drastic decrease in arrow toughness. Specifically, when hitting something hard and the insert and point getting pushed back into the shaft splitting the shaft. Now, every arrow shaft that I buy new must be footed with a 1.5" piece of aluminum arrow shaft.
I remember Charlie Lamb started a thread on footing sizes and it is worth it's weight in gold. With prices rising and quality dropping protect your arrows to the best of your ability. This could also save you from the arrow splitting on a marginal shot.
An added benefit is adding the footing is a slightly increased FOC as most aluminums weight more than your average carbon's gpi.