Marcius
Tribune
Some measure of propriety perhaps? There are a few things in history that particular societies didn't prefer be brought to light, and were therefore left out of their records. In the last example it is mentioned that some tried to protest the executions on the basis of gender, I'm sure there were those that supported inequality of punishment.
Artistic representations of any crucifixion would've been harder to imagine in Ancient Rome than, say, naturalistic scenes of Newgate hangings by Constable or Gainsborough, until Christianity took root.It is a crime to bind a Roman citizen; to scourge him is a wickedness; to put him to death is almost parricide. What shall I say of crucifying him? So guilty an action cannot by any possibility be adequately expressed by any name bad enough for it. -- Cicero
Actually, there is just one ancient visual portrayal of crucifixion I can think of outside all Christian context--the Alkimilla graffito, which is commonly regarded to show a woman.