I wonder what happened that resulted in their tombs being unfinished?
With the kings, it usually happened if they died before the work was finished. In the case of Tutankhamen, for instance, he died before his tomb was ready, so the vizier, Ay, took another tomb (a smaller one) that was closer to completion, had it quickly finished and gave a lavish burial for Tut there. Then Ay kept the original royal tomb for his own burial.