How do you know so much about the motivations of people that have been dead for tens of thousands of years? Maybe you can speak to the dead?
The people from fifty thousand years ago do not differ in any essential way from the people of today, except in the knowledge and in the set of skills that they were taught.
Most human societies that have not seen a writing system at other people have never invented any writing system.
All those that are likely to have invented writing independently (though for some of them it is not certain that they have not seen the writing used by others) have invented writing systems in contexts similar to those of Mesopotamia and Egypt, i.e. in a settled agricultural society where cooperation was required at a large scale and management and accounting of resources was necessary.
I get what you're saying, but I also think it's hard to overstate how different ancient cultures and experiences made people.
If you're a nomadic hunter-gatherer tribe, you're not going to carry around clay tablets that say "Happy Birthday, love Gramma" on them.
Their point is that hunter-gatherers or subsistence farmers have no use for a writing system. A complex urban society does.