Underage does not seem appropriate here. Giving money in the hands of kids is a wrong thing to do but I guess most users are going to be of age in this sector. Kids should focus on building their career and education first to get a stable job.

Solar panels are expensive - the major concern of mining is to reduce the investment so as to maximize the ROI. You are not going to buy something that costs too much reducing the budget allocation to something else. Some miners are using it but they have much bigger farms and the number of ASICs here are making the difference.

Even then, with the huge hashpower struggles between mining pools, indie miners have very little scope to ROI. On the other hand, buying bitcoin is way easier.