> I think it's partly because most bullies grow out of it, and partly because as an adult you're usually afforded the agency to leave situations where you're being bullied.

It is because you can defend yourself. That's all there is to it. If you can defend yourself, people will not mess with you.

Parents that leave children into "schools" so they can get "bullied" and nobody protects them are committing cruelty of the highest order I can imagine.