As the tribe grew and spread out and became more tribes, they found problems with the stories they drew or painted. Rock obviously wasn’t a portable medium so as tribes moved on, they didn’t have the original cave drawing or painting handy. They had to rely on visual or oral reproductions, which weren’t often close to the original.
Also, there were tribespeople who were better than others at remembering a story, let alone telling or drawing it. If your tribe didn’t have someone with these talents, you might have to learn the story of “how to hunt” on your own — redoing, in effect, what had already been done. (Which brings up a good question — what did people call “reinventing the wheel” before there was a wheel?)
Furthermore, the best hunters and gatherers were inadequate storytellers, at best. They needed to do rather than teach. It follows, then, that the best storytellers and painters — the prehistoric content developers — weren’t necessarily the best hunters.
Crude as the cave paintings were, they didn’t stand up well over time — especially if you didn’t have the original story to go with them. One or the other might be adequate but together, they were infinitely better at conveying the entire story. A picture without context, like a story without illustration, doesn’t hold as much meaning. It’s open to interpretation.
And don’t forget — much shorter lifespans, on average, meant that the accuracy and vitality of most stories was quickly lost and never regained.
Mainly, though, the old ways of communicating could not keep up with change — and the biggest change was civilization. When specialized tools, domesticated animals, and domesticated humans evolved, the need for documentation evolved with them. Suddenly, everyone wanted to know “how much?”
Individuals and tribes gained “property”. They needed to know how much land they held, how many goats were in their herds, how much grain it took to feed a person (or a goat), and so on. Predators and poor management were a threat to a herd’s size and the tribe’s prosperity. Plain old tribal knowledge was losing its importance. A better way of communicating was needed.
Next, the saga continues with the importance of counting, numbers, and writing. Until then, take care.