Sam Witwicky: Fifty years from now, when you're looking back at your life, don't you want to be able to say you had the guts to get in the car?
Sam Witwicky: Miles? Miles, listen to me. Listen. My car, it stole itself, okay?
Miles: What are you talking about, man?
Sam Witwicky: Satan's Camaro. In my yard! It's stalking me!
Optimus Prime: With the All Spark gone, we cannot return life to our planet. And fate has yielded its reward: a new world to call home. We live among its people now, hiding in plain sight, but watching over them in secret, waiting, protecting. I have witnessed their capacity for courage, and though we are worlds apart, like us, there's more to them than meets the eye. I am Optimus Prime, and I send this message to any surviving Autobots taking refuge among the stars. We are here. We are waiting.
Trent: Didn't you try out for the football team last year?
Sam Witwicky: No, that wasn't like a real tryout. I was researching a book I was writing.
Trent: What's it about? Sucking in sports?
Sam Witwicky: No, it's about the link between brain damage and football. It's a good book. Your friends would love it. It's got mazes in it, coloring areas, pop-up pictures. It's a lot of fun.
Sam Witwicky: So, listen. I was wondering if I could ride you home. I mean, uh... Give you a ride home.
Sam Witwicky: I bought a car, and it turned out to be an alien robot. Who knew?
Judy Witwicky: [To Sam.] Oh, for Pete's sake! You are so defensive! Were you masturbating?
Sam Witwicky: No!
Judy Witwicky: Well, we don't have to call it that word, if it makes you uncomfortable. We could call it.Sam's Happy Time.
Maggie: What's going on?
Defense Secretary Keller: You're coming with me. You're going to be my advisor.
Glen: Me too?
Defense Secretary Keller: Who's this?
Maggie: He's my advisor.
Defense Secretary Keller: He comes too.
Ron Witwicky: I got a little surprise for you son.
[Drives by a Porsche dealership.]
Sam Witwicky: No, no no, no no! You got to be kidding me!
Ron Witwicky: Yeah, I am. You're not getting a Porsche.
Starscream: I live to serve you, Lord Megatron.
Megatron: Where is the cube?
Starscream: The humans have taken it.
Megatron: You've failed me yet again, Starscream.
Sam Witwicky: It's a robot. But, like a different...you know, like a super advanced robot. It's probably Japanese. Yeah, it's definitely Japanese.
Mikaela Banes: This car's a pretty good driver.
Sam Witwicky: Why don't you sit in that seat?
Mikaela Banes: I'm not gonna sit in that seat, he's driving!
Sam Witwicky: Maybe you should sit in my lap.
Mikaela Banes: Why?
Sam Witwicky: Uh...I have the only seatbelt. Safety first.
Sam Witwicky: This... I can't do it anymore.
Judy Witwicky: What?
Sam Witwicky: You're putting girl jewelry on a boy dog. He's got enough self-esteem issues as a Chihuahua, Mom.
Judy Witwicky: That's his bling.
Jazz: What's crackin' little bitches? This looks like a cool place to kick it!
Sam Witwicky: How did he learn to talk like that?
Optimus Prime: We've learned Earth's languages through the world-wide web.
Chosen answer: There is no reason to think they can't. They simply choose not to. They may feel it's too deceitful.
Actually in this movie (when joining up with bumblebee and the others after they pick up the All Spark) and Revenge of the Fallen, Ironhide uses holographic humans in his cargo bed. Also, Arcee and the twins use holographic drivers at the beginning scene in Revenge of the Fallen.