Why we write things down...?

So...Why do we write things down?
I rarely write things down, I mean I'd like to say I keep a lot of things up top (in my dome)...but come to think of it, my earlier college years have truly hindered that capacity.
I guess I write down things like numbers, names, song titles to recall later...So, basically to remember things...Yes, I would say that this would be the root answer to the posed question.
We write things down to remember them.
When Herotodus started writing things down he, quite literally, invented history.
If William Shakespeare hadn't written things down modern literature would be an emptier, colder place.
But whether we are writing down groceries, or legal contracts, or self-indulgent blogs...we are doing it to be remembered, either by us or for generations to passs.