A question that's been in the back of my mind for a long time is what happened to 9V transistor radios? My first radio as a child was a small, red AM-only Radio Shack radio that ran on a 9V battery. Listened to a lot of baseball games on it.

Did 9V radios disappear because voltage boosting circuitry is so cheap and common now? Or do the components just require less voltage than they used to?