I just wanted to add something to my earlier post. It may be that playing a guitar is highly noticeable. You can't practice often without everyone around you hearing it. Even if you became skilled, there is the expectation of performing in front of people, and most intelligent people feel they need to perform at the top level.
Drawing however allows you to practice in private and present only your best work. Which allows the ego and social standing to stay intact. Everyone has an identity that they make for themselves but often it limits them to always stay between those lines, especially in front of others.
You can go too far in the other direction and burn out an intelligent child for the rest of their life.
There is some balance between allowing them to build confidence with some A's among their peers, and then also being challenged to get that C they didn't think was possible.
Nobody can always function at 100% anyway and both experiences build different skills. It's like how you can't lift heavy weights all day every day. You need down time and stretching as well as aerobic exercise if you want to be able to make full use of the strength.