To me it reads that, since many people already believe this is more about tracking than safety, they are focusing on a device which is the perfect surveillance system, and which conveniently already accounts for 7+ hours of many peoples daily computer/internet interaction.
A desktop computer doesn't necessarily have a microphone or camera, and doesn't necessarily have to be connected to the internet. I'd wager most crime, including that which affects children is done on "disconnected devices" in this sense.