It isn't about protection. It is about values and moral principles. Parents can teach children tools about self control and mindfulness about evaluating if things are good for them or not. Teens and young adults have to explore and figure out their place in the world apart from their parents, but the skills and values taught are often transcendent of the shifting values in culture.

Let's face it, powerful forces in our society discourage self-control and critical reflection, and culture encourages people to have children regardless of whether they have learned those skills

“culture encourages people to have children…”

That’s not true in any western country :)