The story I last heard about the origin of writing goes something like this:

- people use clay tokens to keep track of their herds/inventory

- these tokens get put into clay balls for security/transaction grouping

https://en.wikipedia.org/wiki/Bulla_(seal)#Origins

- to avoid breaking and remaking the clay balls all the time, people record on the outside of the ball symbols indicating which tokens are on the inside of the ball

- at some point, some bright person realises that all you need to do is make the second set of symbols on a tablet; as long as you have them recorded, all the balls and tokens are just legacy