I think the question assumes that gambling is automatic in pool. This is IMHO one of the notions that harms the sport.
The first notion should expect that there is no gambling at all as part of the sport. Any gambling is in addition to or ancillary to the sport. Yes, I know how hokey that will sound to many, but I really believe that.
The gambling notion as a whole, regardless of whether it involves pool, should only be engaged in after a person is an adult and has their own financial means I think, so age is only part of it.
By the same token, if I found out for instance that my college age child was gambling while I am contributing the brunt of their financial support then I want my percentage as their stakehorse if they win anything. And I would collect it, for sure.
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Amen! I do not play for money, and I never want to. I have so much fun enjoying this sport, why would I want to ruin it and make it about money? I took a co-worker up on a very cheap bet; 1st to 5 for 20 bucks, and it was not a fun match. The denomination was clearly not an issue, but we ended up playing chicken-shit safety pool instead of having fun and taking the risky shots. If my kid wanted to wage money on any sport, I would question where that even came from, because it certainly was not from me.