I’ll agree that the kits are cool and have the potential to interest people. I still think a more user-friendly interface should be of top priority to keep those kids from being scared away. I think a significant number of users are turned away by the complexity of mission planner and the documentation’s ties to it.
Bringing this back around to answer the original question, I think ardupilot isn’t attracting many new people because of Mission Planner’s learning curve. That relates to kids. They don’t want to watch a youtube video explaining everything – they learn better by clicking buttons and using everything available to them on the user interface.