Most writing on paper is short lived, and it is generally inaccessible while it is retained. For example, a lot of writings authored by lawyers such as contracts, mortgage documents, etc. have specific retention requirements, and they are destroyed upon expiration.

Even in categories such as fiction, there is no reason to keep every novel written. Only a tiny percentage have enduring literary value.

For society, as for the individual, forgetting is an important process in maintaining sanity.