In your opinion, why is society, teenagers in particular, so materialistic?

Personally, I think its about who can be cooler or more popular. What kind of car you drive, what you wear, are you hanging out with the "popular" kids, do you drink, are you a trouble maker... all that adds up to be who you can be and who you are seen as in school. Because something is popular, they want to conform to it. Like when Brittany Spears sister had a kid, all these teenage girls suddenly wanted a kid; when guy or girl wants to conform, they do stupid stuff like smoking, doing drugs, getting trashed, having babies. Teenagers want to copy images they see of celebrities on any show. Its Human nature to want to be accepted, but people take it way too far sometimes.