Is something that is not used worth keeping?

Would it cause clutter, or would it be better off as a memory? When a language dies, I absolutely think that something is lost. Language has very much to do with the culture it belongs to. There are words for certain things, ideas, philosophies, etc that may only belong to that particular culture. I think the greater question though, is if a language is lost, was it really still useful?

I don't think it's particularly damaging to let a language die a natural death. If it's no longer useful to a culture, is it worth being saved or revived? Unfortunately, not all languages that have gone extinct have been able to be documented, but if possible, the documentation of a language can give great insight into the culture it was used in, and the relation between other cultures and languages. But does it need to still be actively spoken to remain culturally relevant? There is a point where a language may become somewhat of a hinderance and prevent a culture from evolving, like the previous poster said about old english. What kind of society would we live in if the language was preserved the way it was for centuries instead of changing?