Preppers have historically had distrust for computing technology. Y2K was a real risk, but since it seemed to be overblown, a catastrophic computer-centric risk has fallen off the radar of many. A cyber attack should rank up there with many other potential Black Swan risks (solar flares, economic collapse, etc).
Today, most everything the average American depends on to sustain life is run by some computer or another. Some examples:
• Wal-mart or your local grocery store cannot provide just-in-time food delivery to it's stores without complex computerized logistics systems.
• Your municipality cannot pipe water to your house or sewage from your house without computer-controlled pumps.
• Your bank cannot issue you paper money or process credit card transactions without computerized accounting systems.
• Your electrical and gas provider cannot provide power or heat to your house without computer controlled generation and distribution systems.