Hi Charlie
You are absolutely right, however, it is one thing for a person to stand in the street with a camcorder filming, it is obvious that sound is likely to be recorded and people observing this are unlikely to divulge any personal private matters in front of your camera. With CCTV on the other hand it may not even be immediately obvious that there is a camera present, and even so, there is still no reason to assume that audio is being recorded. Therefore if allowed, CCTV could capture audio that was intended as private but not unlawful. In the UK we put signs up to warn people that CCTV is in operation, if people ignore the signs and continue to break the law then they deserve everything they get. But people that are not breaking the law and going about their everyday business are entitled to have their conversations kept private. The whole purpose of CCTV is to deter or capture crime, not invade peoples private conversations.