In Shakespeare’s times, noblemen were rarely killed in battle; usually they were captured and ransomed for a large sum. That’s one reason not to kill their “prize”. Antony is also aware that his struggle to gain control of the empire will not end with the defeat of Brutus and Cassius; there is still the obstacle of Octavius. In his upcoming struggle with Julius Caesar’s designated heir, Antony will need the support of nobles like Lucilius.