"Once we've destroyed the Earth, collect the energon and bring me all of the humans' sparks as well. I think I'm going to use them to create a new batch of soldiers for my army."
"But, sir. You can't do that."
"Why not?"
"Well, the humans' spark is fragile."
"WHAT?! Impossible! Their spark's not eternal?"
"One life. That's all they've got."
"Bahh. Then they really are poorly designed."