Age
Short one- there are cultures which operate strictly on age. From birth, a child is presented with a list of chronocentric milestones- when he/she becomes a man/woman, when (s)he can be married, do different things, gain titles, etc. Our society, however, allows for individual development. Pretty much, you become a man when you show the qualities generally accepted, not when you've reached a certain age. This allows for younger members of the society to contribute at a potentially lower age, and it also doesn't give the honor of 'manhood,' like a title, to those who don't fit the requirements. I appreciate it, mostly.