Why exactly are teenage girls addicted to Starbucks?

I'm a guy in highscool for reference.

Everyday there is at least one girl who apparently went to Starbucks before school (before 7am) to get some sort caffinated beverage, who is bringing them, when they are going, and why they are getting up so early to get Starbucks is beyond me.

Is this some sort of weird social pressure to like mediocre coffee? It's seemingly especially common for the "basic" blonde, popular, girls to have some sort of obsession with the... restaurant (I guess) to have an obsession with the drink.

What kind of addictive substances do they put in their products (MSG, sugar, ect)?

Is there some other reason besides addictive substances thst explain this obsession?