Underaged gambling is a developing problem because of the presence of online gambling and the availability of mobile phones for the underaged, you will be surprised that they also watch pornography and visit sites that are not appropriate for their age. I think that the first place to start to discourage them is through the home, parents shouldn't buy smart phones for their underaged children and they should monitor how the children access their phones. If you regulate how your children use your smart phones by monitoring their activities on phones it will discourse them from accesing sites that are not appropriate for their age including casinos.
It is very difficult to overcome, to the point that they even falsify data because every gambling site also enforces a 17+ age limit to register. However, in the environment where I live, I see many minors playing online gambling through their phones. So indeed, there is only one way to eradicate it, which is supervision from parents and also the immediate surroundings. If they are unable, this will damage the generation because in gambling there are many considerations, and minors are not yet able to control it.