It's not even an issue of "orphaned works." Every work becomes Public Domain eventually; that's the point of it.
In fact (according to originalist American sensibilities, at least) the entire point of copyright law is "to promote the progress of science and the useful arts" (i.e., to enrich the Public Domain) to begin with! Allowing works to be copyrighted (essentially, borrowed back from the Public Domain temporarily so the creator can profit, thus incentivizing the creation of works) is merely a means to that end, not some sort of moral entitlement.