Because sheltering children does not educate them to deal with life, and is in my mind one of the reasons so many kids commit suicide. Pretending your children live in some fantasy world where there is no violence, bullying, or pedophiles, leaves them unequipped to deal with real life threats to their wellbeing.
You also have to think, WWE does random stopovers at some schools(not all, as there has never been a B.A. Star assembly this side of the border), and they are lucky to reach 50% of the students in attendance, most likely only the kids who are being bullied(which could even bring the percentage down tremendously). The bullies are just going to laugh, and joke about the whole thing, and the people who are not being bullied, but are not bullies themselves probably don't care. You eventually wind up with a percentage of a percentage of the target audience even listening. Because the target audience is in fact the bullies, B.A. Star does nothing to properly equip children being bullied, because they cant tell kids to fight back.
Then there is the fact that you cannot fight someone else's battles for them. You can give them the tools, and the knowledge to deal with it themselves, or you can get involved, which only makes matters worse for them when you are not around. This makes your fight, no matter how noble it may be, a lose/lose situation.