lilmod, what I’m suggesting is that the age of adulthood among us Jews being 13, the goyim currently(*) consider the age to be 18. What we start at age 20 you might say the goyim start at age 21, when they, too, have additional milestones of adulthood to be considered attained (i.e. alchohol, gambling, adoption.)
(*)give the goyim another decade and they’ll raise the age again as they continue infantilizing young adults and not hold them responsible for their actions.