Coding in itself is a bit hard and stretches our imagination while being fun and challenging. It's much more difficult to learn to code as a self study. Especially children generally need some hand holding and predisposition before they pick up and start coding themselves.
Self study is great once a sufficient amount of grasp of the fundamentals of coding is gained from a teacher or guide. Many think we don't fully understand when we self study or perhaps may take a longer time to grasp. During this long spell of frustration of not seeing results many kids give up coding and they never take a second look at this extremely rewarding super power.