Children are being adultified because our economy is depending on them to make purchasing decisions. So they're essentially the victims of a marketing and capitalist machine gone awry.
The liberation children experience when they discover the Internet is quickly counteracted by the lure of e-commerce web sites, which are customized to each individual user's psychological profile in order to maximize their effectiveness.
I do remember the moment when, as a child, I realized that the things we call 'TV shows' are really just the stuff that gets put between commercials. Later, I came to see that the kinds of things that get on 'free' TV are shows that help sell products.
Marketers spend millions developing strategies to identify children's predilections and then capitalize on their vulnerabilities. Young people are fooled for a while, but then develop defense mechanisms, such as media-savvy attitudes or ironic dispositions. Then marketers research these defenses, develop new countermeasures, and on it goes.