For whatever reason, many people are many learning ASL... it is not difficult or expensive to learn this unique form of communication. It's even exciting!
You can communicate clearly with ASL at distances far beyond the reach of the loudest shout!
Underwater divers use sign language to communicate with each other, in an environment where speaking is often impossible.
A very small microphone can pick up and eavesdrop on any spoken conversation, even if whispered. But a microphone is useless at recording sign language!
Yes, it is true that a video pickup COULD record it. But the recording would have to be continuous (not a sequence of still-shots) and in well-positioned direct line of sight. A video camera would be useless if the person speaking American Sign Language was behind something or had his back to the camera...
