Agree with @DroidsLookingFor and the others saying that yes, investing as something a kid is interested in is good to highlight on an application, if it really is something that’s a strong interest.
In addition to all the good reasons listed above, some schools have investment clubs, and participate in investing contests. Schools are looking for kids who will be involved. Personally I think investing is great. There will be orders of magnitude fewer kids who are passionate about investing applying than violin players, or model UN participants.