I do agree with what you're saying, but i think one big element which is easy to overlook if you're not a teenager your self is the influence of social media. I am 30 years old, and don't really know what's going on.My nieces came to stay with me for a few days this week who are 10, they we're watching things on youtube that made me raise an eyebrow. Nothing crazy but makeup tutorials, meme videos, and a lot of what i saw i wasnt happy about. So add on a few years, teenagers have laptops, smart phones, ipads, they are bombarded with information from across the globe about what other teens are doing for fun, hypersexualisation, ideals and standards of beauty. I actually watched a kids tv show with them, designed for their age group and it had 14 year olds in it who were clearly much older teens, fully dressed and dolled up like adults, partying, i thought to my self wow, how many parents actually pay attention or are even aware of what apps, games, tv shows their teens are watching and how this may be influencing them regardless of the parenting skills, they quite literally have the whole world in their hands and parents aren't the only people with significant influence on their kids anymore.