Why do you have to be 18 to do the lottery, and 21 to go to casinos?

Sorry if I got a number wrong there. But why so high? I'm 15 and I wanna do blackjack! lol. if I was with my parents would I be able to play? And like with the lottery too.. what, they'd be jealous to have kids/teens be millionaires? its not like adults are going to always use it for a mature reason anyways, so that would be a dumb reason. maybe it could go to a trust fund for when the kid is older or the parents decide how they're gonna use the money, or they just give it all to the kid! I'm not saying any age. How about.. age 15+. If I won the lottery, I'd go shopping, help out my family, help out my extended family, help Cameroon (I'm Cameroonian), er....... save some for college for me, family members, and other relatives.. I'd save a lot. I'm not stupid and wouldn't spend it on drugs or whatever, thats for losers honestly. I'd also donate for better hospitals and schools around the world. I mean world hunger is bad but if everyone eats but doesn't get a good education in school, or dies from diseases, isn't that a waste? Its good that they get food but I'll donate for other things. I would kick , yo. haha.. YUPPPPPPP so I should win that thing.. if I could. Scratchcards.. its so hard to win at them. The lotto is easier. Quick pick, yo. DOn't take everything I say here seriously, haha I'm not dumb or anything, just joking around sometimes.