Sure, you could just throw your trash away. But then how would you let all of that pent up aggression out? Not in a healthy way, I bet. A healthy way like beating up a bag full of trash.
The Do Box punching bag is a mix between a punching bag and a garbage bag. Fill it up with compost or garbage, hang it up, and go to town. When you're done, empty it into the trash and fill it up with new trash. Makes perfect sense!