Why are bullied told to move on instead of parents teaching their kids not to bully others?

I wasn't ever bullied but this has me wondering. Society and others expect bullied victims to just move on with their life as if nothing ever happened, clean the mess their bullies made and succeed in life. While I don't deny that's important, the parents of the bullies generally defend their kids and don't do nothing to stop it.

Why are we just focused on the bullied victims moving on and not on parents actually doing their job in teaching their kids not to bully others?
Why are bullied told to move on instead of parents teaching their kids not to bully others?
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