Optimus always did his best to understand humans, trying his best to understand their language, biology, and many other things. But he never quite understood one thing...

Human life. Autobots were near immortal, age wasn't something they worried about. So a life as short as a humans was a foreign concept to him.

"Humans live so little..." *He says, not knowing how to word the question he wants to ask "Why is your life so short?" he asks. You're human, you should know why, Right?