This is low-hanging fruit for reformers. When a Death Certificate is filed, every single financial account you have is de-activated the next morning. Stock accounts, bank accounts, credit cards, etc. Dad's check to the electric company got deposited the same day? Too bad. And that's just for starters. It all happens automatically via the big computers in the sky. It is a simple matter to add each state's voter registration computer to the list, and I am both surprised and appalled that it hasn't been done.
I’m not sure what you meant by “de-activated.” The executor of a deceased person’s estate is generally obligated to pay the outstanding debts of the deceased. Of course, some debtors don’t make claims. If there aren’t enough assets to pay all of the claims, the executor decides, consistent with applicable state law, who gets paid. Some assets like retirement funds and insurance payouts to heirs are usually not subject to debtors’ claims.