[semiquaver]

  > People do care about income streams for their descendants or charitable organizations

Society created the concept of copyright and intellectual property for a reason and it is emphatically not the protection of income streams after you are dead. Whether a person exists who cares about a thing is not a reason to preserve it.

[Retric]

That reason was to generate more works.

Before the conception of copyright artists would create physical works to be sold after they died to support their families in part because such works would be more valuable after they died.

Indirect effects matter both for society and as a legal question. To this day many elderly / sick artists are working not for their own personal interests but for other people.

Thus copyright not expiring as soon as people die is supporting the original goal of copyright. The total length of copyright is a different question.