The difference is humans can see the visual spectrum but not the radio spectrum. This means that people tend to ensure their own privacy in the visual spectrum

The difference is humans can see the visual spectrum but not the radio spectrum. This means that people tend to ensure their own privacy in the visual spectrum (by wearing clothes, etc), but don't in the radio spectrum (by transferring sensitive data unencrypted). You could argue that people are being irresponsible by not paying more attention to their "radio privacy" (and you'd be right), however the lawmakers apparently felt that the advantages of making it illegal outweighed the disadvantages.