If you are a shooter and you spend a lot of time in the gym it can get monotonous shooting catch and shoot shots without some kind of challenge or game. You want to find ways to keep mentally engaged and locked in on each shot. This shooting drill is not ground breaking by any means, but it is a great way to mix it up and keep the shooter excited and locked in while shooting. If you have multiple players shooting it will help to promote a level of competition as well.
Along with being a great way to keep players engaged, it will also help to teach shooters to be able to make shots with some pressure on them. You can't ever completely replicate game pressure, but learning to shoot with some type of pressure on you makes a big difference.