Changing ball trajectories accurately is hard but you are editing something in motion that is visible only for a few seconds, is in air, and will mostly be viewed through a bad screen. Adding in cg bins on the other hand, you need Beckham to do 3 kicks that land where the shot is looking, but more importantly have to get those cans tracked perfectly for the entire duration of the shot as they are always visible. I believe that is a much harder to pull off.