The vast majority of artistic output results in having little lifelong, let alone postmortem economic value. Most artists glean all they are going to get out of their art within a couple years of its production, and the idea that it will sustain their families is silly. In the small number of cases of phenomenally successful artists, they usually make enough to sustain themselves and family, but even still, the benefits accrued to outliers should not be sufficient reason to significantly slow the pace of artistic progress and cross-pollination of ideas. Besides, in any other situation in which wealth is bequeathed, that money must have been earned already. Copyright is a bizarre construct that allows for the passing on of the right to accrue future wealth.