And it's not as entertaining either.
The entertainment value of public executions, especially if carefully thought out to be visually exciting and horriffic, would be immense. The income to the public treasury from selling live feed on pay-per-view, with the follow-up syndications and spin-offs (imagine the coffee-table Time-Life book "Great Executions", with broadsheet-sized full-color photos of the carnage...now THAT would sell!) would be enormous.
There'd be "REAL Justice League" trading cards sold with bubble gum: "Oooo, Oooo, I'll trade you a Jeffrey Dahmer impalement and a John Wayne Gacy crucifixion for a Unabomber boiling and a Suzanne Smith drowning!"
Think of the boost to commerce and to the general civic respect for law and order! Think of the receipts.
Unfortunately, all of the interesting ways to kill criminals destroys their bodies and makes their organs unusable...WAIT! I have the perfect solution for organ harvesting AND revenue-maximization from gory public executions: Death by vivisection! We execute death row inmates BY extracting their organs for reuse, flaying them for their skin, etc.! That would provide all the screaming and drama anyone could hope for AND would provide good organs for use! Why didn't I think of that before!