I disagree with your implication the age of adulthood is steadily rising. In reality, it's just fluctuating. The US's age of majority was 21 until the need for

I disagree with your implication the age of adulthood is steadily rising. In reality, it's just fluctuating. The US's age of majority was 21 until the need for soldiers in WWII drove it to be lowered. Other cultures have gone even higher.