Cyberpunk creates a dense world for the reader to explore. "Johnny Mnemonic," by William Gibson, is an example of this. Gibson does not lead us by the hand and talk us through the world before getting into the narrative. It drops the reader headfirst into a world that we don't fully understand.
Generally, I feel this is an effective technique for a short story. In this format the reader doesn't have the time or patience to sit through a long piece of world-building exposition. Gibson lets details of the world slip out through the narrative. The first hint that this story is set in a cyberpunk world is when Johnny describes himself as a "Caucasoid."
I feel the first paragraph is almost deliberately misleading. Johnny is putting a shotgun in an Adidas bag with tennis socks. These are all things that exist in the real world, and a reader that didn't understand that this is a science fiction story may be thrown when Gibson describes the world throughout the story. This is a good setup for the piece because it keeps the reader on their toes. The reader understands that they have to look at every detail and fully absorb the piece if they want to understand it.
The other benefit of little or no exposition is that it lets the writer get straight to the action, which is usually the most engaging part of any narrative. In "Johnny Mnemonic," the first line has Johnny getting a gun ready. This immediately raises the stakes and engages the reader. If you see a gun in any story, someone's probably going to be shot. The reader immediately wants to know who and why.
I feel that these techniques give Gibson the ability to pull the reader into the world and the narrative straight away. It diminishes the importance of the setting, but it's still necessary for the reader to understand the setting. Gibson layers in this information about place and time as the story continues, after he's already hooked us.