How much access to money parents want to give their kids is up to the parents.
What people do with their own money, including kids, is up to the people.
WHY are countries not enacting laws that punish companies for once? Say something like:
• "After 3-5 purchases of the same item with random contents the buyer should get the content they specifically want."
• "No item with random contents should cost more than N $\€"
• "Buyers should have N-M hours to get a refund for an item with random contents"
That way you could keep the "fun" and spirit of gambling without its destructive spiral and stuff