It's common for linguistics consultants to request that recordings be held private for a certain span of time after their deaths--- that may be one factor.
Another thing that is a factor for certain communities is that some stories or songs are the cultural property of particular families. In that case, older members of the family may make recordings to be held for when the descendents are ready for them--- when they're old enough, or perhaps when the language has been revitalized so that people can understand them again.
Another thing that is a factor for certain communities is that some stories or songs are the cultural property of particular families. In that case, older members of the family may make recordings to be held for when the descendents are ready for them--- when they're old enough, or perhaps when the language has been revitalized so that people can understand them again.