If the jury can get it wrong, why can the prosecution not be wrong?

When a verdict comes down like that in the Casey Anthony trial people want to think the jury got it wrong, they don’t want to change gears and believe what they thought was wrong, but that the suspect is still guilty but got off. Many people lose dozens of years, some on death row, until evidence, sometime suppressed by the prosecution, or DNA proves the convicted could not have done it. Even with that proof, why are people so slow to say the prosecution messed up and stole many years of freedom from an innocent person while the real criminal got away? It always comes back to the person was still actually guilty but got lucky, and were sprung on a technicality. Is it so hard to say the prosecution made a mistake?