Well that's the question isn't it, agency but to what extent. It makes sense to allow teenagers to have more agency over themselves than a 10 year old, but clearly there is an argument for limiting their agency on social media platforms.

Just because there are adults that abuse their agency of the use of alcohol (alcoholism) doesn't mean we should remove restrictions on young people.

Just because there are adults with full agency who drive recklessly doesn't mean we should allow 13 year olds to drive cars.