As others have mentioned, footing increases the strength immediately behind the point. Actually increases the strength the entire length of the footing. I haven't experienced footings breaking four-six inches behind the point.
Normally, a standard length hardwood footing on a softwood (cedar) shaft will add about 20-30 grains. That translates to about 1-2% FOC, so you don't gain much FOC by footing, unless you go with a particularly long footing. The reason you don't gain much FOC with a standard size hardwood footing is you're just replacing the cedar that was already there (and had weight of its own) with hardwood. So your weight gain is not the weight of the hardwood footing, but rather the difference between the weight of the cedar that was already there and the weight of the hardwood footing. But, they look cool and do make for a stronger front end of your arrow.