An aspect of shooting that many (including me prior to this) don't even consider is the movement we will have naturally as we hold a pistol and pull the trigger. We are not robots, or machines, we are human beings with a pulse so it is natural for us to have a slight movement that translates into a dispersion of shots that increases the further away from the target we are. 

Example: Shooting at 3 feet the dispersion of shots is going to be pretty tight, but the same movement from 25 feet will translate into a much bigger dispersion of shots. 

Thanks for listening, 

Matthew