if later children can get 1 bitcoin not with their own competing results it can be with the help of others or even from the parents who buy it if the child is very clever then this becomes an asset in the future because bitcoin is not always in the price now competing for the next few years will go to the price.
At the early stage of bitcoin, you can earn it thru playing video games as a reward and since it's not yet popular those teenagers had to intention to keep it since it has no value other than use it to play video games. I remember a person said that at that time he has 20 BTC which he gained from playing those games and without thinking that those coins will become valuable after 9 years. Lucky those teenagers who manage to keep their bitcoin and sell it at higher price.