The disappearance of a language may seem like an unfortunate loss only to the people involved. However, the impact goes beyond the losses of particular bits of information, like Indigenous names for medicinal plants yet to be classified by scientists outside a community, or concepts and worldviews reflected in the words and structures of one language that do not have parallels in another. Understanding language is vital to understanding human cognition.

Each language is a piece of the puzzle that we need in order to determine how language works in the mind. With each missing piece, we are further from seeing the full picture. Analyzing these patterns is far from an esoteric academic exercise. The more we understand about how language functions, the better equipped we are to improve our therapies for communication disorders and our methods for language teaching. Early models of grammar were based primarily on a few large, mostly European, languages that Western scholars knew or could easily access. Imagine the deficiencies if the research stopped there. It would be like basing an understanding of plants on a neighborhood vegetable garden or of animals on a trip to a petting zoo.

Documenting a language thoroughly is a major undertaking involving years of collaboration between the members of a speech community and linguists (who may or may not be speakers themselves). Given the rapid rate of language loss in the world today, many languages are in danger of disappearing before they have been documented, taking with them irreplaceable information about human cognition.
—Anastasia Riehl (8 Nov 2019) "Why Are Languages Worth Preserving?" Sapiens