While this is a sound theoritical advice, the real world has changed a lot. Parents and elder siblings are not the only people kids interact with. For every parent mindful of dangers of unsupervised internet access, there are many parents who give unrestricted access to tiktok (and rest of the internet) because everyone other person does that, and then kids share.

Businesses don't care for the careful minority when they know such advices will be shared, silencing those who really care.

Even the feature name "parental control" is chosen to induce guilt in parents.