Not cost effective which is the reason why Alcatraz was shut down as a federal prison.
Everything must be brought in. Even if the prison was restored to the same condition when built, which it hasn't been, the prison authority would still have to bring in food, water, fuel (for generators) and everything necessary to operate a prison. Alcatraz also housed the guards' families and the kiddies caught the boat to San Francisco to attend school (Alcatraz is within San Francisco County lines). Housing for guards would have to be rebuilt (Indian occupation burnt it leaving the concrete shell). San Francisco County Jail #3 had a farm (drunks/bums) that grew vegetables for the jail, the county hospital and when there was surplus, Alcatraz (bet nobody here knew that).
Last tidbit: the Civil War casemate still exists beneath the prison. It's not like the movie. The caponiers are still there too but there is no access as it's a bird breeding ground and the NPS don't want to bother the birdies.