Obviously because if you learn and grow you will have a mind of your own and will be able to decide FOR YOURSELF what is worthy and what is unworthy.
THE ONLY WAY they can stunt the growth and maintain control over their kids is to keep truth away completely. Replace it with lies. That when they are adults they will do the same with their children and it will be the legacy of stupidity idiocy ignorance their descendants will live by forever more.
A mind is a terrible thing to waste.