The best question there is: why? (Particularly when it comes from a 5 year old.)
In this case, why do we teach kids martial arts? Well, movement is good. We all know that one – but that doesn’t address martial arts specifically. Why teach a fighting art to children?
On the other extreme, we could try and argue that we’re teaching kids to defend themselves in case they get attacked. That’s definitely specific to martial arts and certainly, right?
Let’s take a middle ground, and talk about it from the perspective of an elementary school playground. Basket balls, jump ropes and limbs fly about regularly on the playground – sometimes with malice but often without. The child who has learned to bring their hands up in the face of an oncoming threat arguably has a better chance of avoiding getting smacked in the face.
That’s a specific reason.
Most folks recognize that training hard in a movement art also allows children to experience adversity within a controlled environment. There are rules, there are goals, etc. This allows them to face adversity in the outside world with greater poise. Martial arts does that too, as well as any other movement art. But what about bullying? Does martial arts offer tools to students that allow them to resist, defuse or ignore bullying more effectively than say, basketball?
Martial arts is the study of fighting. Basketball is the study of scoring points on a specific field and playing within a specific set of rules. Therefore, it follows that (studied and taught properly), martial arts should give students the tools to deal with a bully; Likewise, it follows that basketball should give students the tools to play the game of basketball (obvious, right?). If martial arts doesn’t help a student handle a bully then it is like teaching them a bizarre version of basketball where you never practice shooting the ball through the hoop but merely hope for the best when game time arrives. That might be fun, which is good, but if in learning a skill a student fails in grasping the fundamental focus of that skill then there is no why.