The following is drawn from Johnson 2003 (see reference below).
Language documentation should be archived for much the same reason that it is collected/documented in the first place: there is little sense in collecting data on languages that are disappearing if there is no plan for preserving that data.
Documentary linguists should archive language documentation:
- to preserve recordings of dying languages for future generations
- to facilitate re-use of materials (e.g. recordings, field notes, transcriptions) for
- language maintenance amd revitalization programs
- typological, historical, comparative studies
- any kind of linguistic, anthropological, or other study that you don’t plan to do
- to foster development of both oral and written literatures for endangered languages
- to make known what documentation there is for which languages
You should also archive your language documentation to further your own career, if you are a student or academic. Archiving is a form of publishing: even if materials are archived under restricted access, the metadata is published in the archive catalogue. You can list materials that you have archived on your CV, and cite them in scholarly and other publications. This enables readers to locate the primary materials on which work is based, and also ensures that the speakers whose knowledge and artistry are preserved in the documentation materials are given proper credit for their contributions.
Heidi Johnson (2003). Language Documentation and Archiving, or How to Build a Better Corpus