The idea of giving somebody multiple life sentences also makes legal sense. You never know what sentences may later be overturned.
Let’s say Smith is convicted of killing ten people and given a collective sentence of life imprisonment for the ten murders. And Jones is also convicted of killing ten people but he is given ten separate life sentences, one for each individual conviction.
A couple of years later, one of the supposed victims turns up alive. Obviously the conviction for killing that person is going to be overturned on an appeal.
In Smith’s case that’s going to be a problem. If you overturn the sentence, you’ve got nothing left to hold Smith on. The DA is going to have to hold a new trial for the nine remaining victims and hope that Smith will be re-convicted. Or let Smith go.
In Jones’ case, there’s no problem. The life sentence associated with the living victim can be dismissed. Jones is still being held on the other nine sentences, which were unaffected.