You see, it is not just that person with the necessity to learn this, for how will they communicate with anyone else if they are the only one that knows what the signs mean. But I guess that is "un-common" sense...
What most do not know, however, is that sign language goes back much further than the origins in the 17th century.
There is evidence that Plato wrote about sign language and the deaf, and tried to implement some form of sign language, but of that actual group of signs little is known.
Another form of sign language comes from the 10th century in churches. The Monastic sign languages were a grouping of gestures to display ones needs during vows of silence or during times where speech was forbidden. Used especially in Benedictine monasteries, the signs are described as gestural communication instead of an actual language. However, its gestures are used even today in modern sign language.
It is curious, however, that there is nearly no written records of deaf or mute signing languages being fully developed until the 17th century (the Monastic signs were for vows of silence, not the deaf or mute), even though deaf and mute peoples themselves are referenced.
So, it seems that back then, much like today, deaf and mute peoples were constantly having difficulties communicating efficiently due to a lack of knowledge by the general populace.
Offering a class in our high schools as a second language that teaches students sign and braille would be exceptional and is starting in some select areas.
We are out of the Dark Ages, lets act like it!