Honestly I’m okay with making the age of legal adulthood 25 years, and I’m part of one of the last generations that could buy cigarettes in the US at 18. A long time ago, people didn’t live as long as they do now, so it was just kinda mutually agreed upon that an 18 year old kid was smart enough to read and enter into a contract. Military enlistment? Contract. Marriage? Contract. Home loan? Contract. Can you honestly say that at 18 you knew what you were signing up for with every contract and agreement you were signing?