From most of the ideas I think limiting a child's accessibility is indeed the best and most effective idea to prevent them from exposure to gambling, especially promotions spread on the internet or social media, on the other hand, yes I understand that the government should also intervene in this matter, but yes, especially in my country, the government has indeed implemented new regulations and also always conducts surveys to the community with the aim of reducing the population level of gambling exposure to a child who is still a minor but in the end it does not produce any positive impact, meaning that gambling exposure is still ongoing and even getting crazier and that means it is true as you said that we as parents should take action, namely by limiting a child's accessibility in terms of using a smartphone, none other than because only parents have full access to monitor and regulate a child's activities.
When I was teenager my friends liked to bet a lot and there was no control of age in betting shops, even though formally you had to have 18 years to bet. All of them have grown up in normal people. There is no problem in bettong but there is problem if ot runs out of control.
If someone have affinity for gambling they need to be protected being teenager or not. If it goes out of control it can escalate in mental illness and ruin one's life.
One of the reasons why gambling is not recommended for a minor or one of the reasons why a child under the age of 18 is prohibited from being involved in gambling is because the majority of them are children who are still very unstable and also in terms of thinking they are usually very careless in every time they draw conclusions and also of course in terms of self-control and emotions are still very difficult for them, and if for example it is true as you said that your child and some of your friends did not experience any problems and negative impacts from gambling when you were a minor then of course that's good, it means you already know about how to gamble properly and correctly.
Basically, yes, I understand that this is not just about teenagers or minors, caution and vigilance apply to all gamblers regardless of their age, because it is not uncommon for me to see adults involved in gambling and eventually addicted, the point is to always maintain awareness and use your common sense before making a decision.