Loss of unwritten knowledge
Decline of vocabularies
The undesirability of a society communicating only in an unwritten language is its ephemerality if the language is immaterial (voice, sound, gesture) or its abstractness if it is material (a circle of stones, a knotted string, symbolic colours). In dwindling primitive tribes, the cultural legacies will be lost when members of the tribes no longer understand the unwritten languages. In some countries, the use of a non-latin script for writing is, for the purposes of using modern telecommunications, the same as if the language were unwritten, since the letters or characters cannot be transmitted or entered into computers.
When a language disappears, traditional knowledge tends to vanish with it since individual language groups have specialized vocabularies reflecting native people's unique solutions to the challenges of food gathering, healing and dealing with the elements in their particular ecological niche.