For instance: age of sexual consent, age for legally drinking alcohol, age for driving, age for voting, age for participating in pornography

Depending on the place, each of those requires a different minimum age. Why is that? Are some activities “more adult” than others? Using USA as an example: legal drinking age is 21, legal driving age is 16, age of consent varies between 16-18.

Not asking about different countries/states having different ages, but any single place having different ages for different adult activities