Could someone please explain to me why prosecutors, who will tell you they don’t seek mere convictions but instead “seek justice,” are against measures designed to ensure that evidence used at trial is not destroyed?

Public storage isn’t that expensive, so cost obviously isn’t the issue.

Could it be that most prosecutors care more about convictions than about justice?

Go look up “imputed income”. After you’ve picked your jaw up off the floor and recovered from the induced heart attack at the blatant injustice and essential enslavement involved, hope and pray that the judge who hars this case understands that, as the guy was in jail, he wasn’t making less than he could have by his own choice.