The bench press is a staple among powerlifters, bodybuilders, and gym rats alike.  Many lifters only train the bench press with straight weight, all the time.  Here you see Doc knocking out a set of bench with chains.  

Chains are beneficial because they overload the top of the lift which is where many lifters struggle, especially those that lift in gear. Really taxing on the triceps.This can be used as ME movement or accessory.  Many times lifters use chains on their dynamic effort days.