I own a 2010 Camaro SS and it doesn't have a spare. Part of that because those tires are HUGE -- I doubt I could fit one into my trunk -- but also because the front and rear tires are of different sizes. Which size should you carry?
Chevy also put my battery in the trunk for weight distribution reasons, which makes the available space there even less. Maybe they felt they could do that because there was no spare.
I love my Camaro but it is definitely a "pay to play" vehicle.