I think the details matter here. If you give your child $10 every month to make one bet, sometimes they win, sometimes they lose; you are doing it wrong. If you give them $50 and let them make a series of bets not exceeding $10, they will learn that the curve sometimes goes up, sometimes goes down, but ultimately ends up at zero. Not because "you were not lucky today, but maybe the next time", but because this is how the system works.
It's like Oscar Wilde's famous quote: "As long as war is regarded as wicked, it will always have its fascination. When it is looked upon as vulgar it will cease to be popular."
I'm fascinated by the prospect of receiving a free $20. I'm not fascinated by the prospect of putting my finger in a mouse trap because I "might get the cheese this time". Putting your hand in the mouse trap in front of your kids is not a smart move. The addiction is top down enforced by both large industrial agendas and the parents giving weak unprincipaled stances against the normalization of gambling, or worse, being culturally addicted themselves in front of their kids.
My experience with raising three kids is there’s a limit to the amount of messaging that gets through with any fidelity. So, the only financial teaching I did with them, was the stocks, bonds, diversification, risk and prudence schtick. I could see the attempted teachable lesson about gambling losses going sideways and crowding-out the rest.
I'm sure many parents place proxy sports bets for their kids. Maybe to teach them how to use betting as a form of entertainment and learning how your money can also just disappear. I can see it being a good thing if done carefully. I can also see it going wrong.