So you can't drink booze until 21 (in the US only.In the UK it's 18) you can't smoke till 18 You can fight for your country at 18. It's hard to rent a car before 25. You can't drive a car till ur 16-17. You can't smoke a plant that never killed anyone in most states and in most countries, But you can mutilate your genitals and pump a shit ton of the other genders hormones at any age.