system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes people stop crying like children when they are hurt?
gpt
Crying is a way of signalling help from others, specifically parents or guardians.

Evolution has determined there is a time when animals, including humans, can not generally rely on their parents to protect them.  At this time crying can suddenly become counter productive - as it also signals to hostiles that you are weak, vulnerable, easy pickings.  Screaming is totally different, you're showing your teeth and making a scary sound, pronouncing damn clearly you're still alive and conscious and have fight left in you, and you're basically ready to f'kin rumble.  The opposite of crying.

So evolution slowly determined that around the 14 year mark, puberty, the advantages of crying were outweighed by the cons.  There was more chance a hostile would go for your jugular knowing you're already suffering bad, than your mom or pop would step up to save the day.

Crying also made it more difficult to find a mate - as potential mates are often looking for protection, and you are 'advertising' you can't even protect yourself.  Again, helping evolution start stamping it out.

A variable in this equation is your capability at that age to start helping yourself out of situations.