I think you have to assume that there's kind of an ambiguous continuum between art and writing. Obviously hunter-gatherer bands likely had reasons to communicate with band members, whether by sounds or visual signals. And obviously they made art, and humans being humans, presumably a lot of the art hat some kind of meaning. I think there are uses for using symbols to communicate well before you need ledgers or anything similar. But I don't know exactly where art turns into writing: Even when the world was mostly illiterate, it seems clear than lots of humans had some level of symbol literacy. And in some places that symbol literacy gets so dense you have Chinese or Egyptian hieroglyphs. And maybe in others you maybe have something similar but less preserved.
There is reasonably strong evidence that writing actually evolved out of accounting. These early agricultural city-states needed to track the seasonal collection of harvests from the farmers, and continual distribution of food back to everyone.
What started as a ad-hoc system of tellies, eventually evolved into a fully-fledged writing system. And once the accountants had a functioning writing system, it would have been obviously useful, and moved into other parts of society. Tax records, laws, contracts, long-distance messages, recording history.
Art was probably one of the last places in society actually take advantage of this new writing technology.
Hunter-gatherer societies didn't develop writing because they didn't need accountants.
Or... we've found the most evidence of writing connected to an activity that would have naturally made the most effort to ensure it's preservation.
Thing is, we have plenty of evidence of writing connected to other activities from later periods.
As for the effort, the most would be expanded on preserving monumental projects glorifying the rulers etc. But, again, in the historical record, this shows up later than accounting records.
> Even when the world was mostly illiterate, it seems clear than lots of humans had some level of symbol literacy.
Interesting - where is that from?
Practically all painting or drawing includes some sort of symbolism. Sometimes it’s so obvious that we don’t recognise it as symbolism (picture of cow = cow), but other things aren’t (spiral = ?).
The Wikipedia article on Rock Art contains a lot of discussion on the meaning of ancient drawings, for example: https://en.m.wikipedia.org/wiki/Rock_art
More recently, medieval painting has a lot of symbolism modern audiences can no longer “read”.
I read about an American professor that was visiting the various cathedrals in France and started noticing that the stained glass windows were interweaving the parable of the good samaritan with the story of the garden of eden in a fairly consistent manner. He didn't understand why they were doing that until he found records of medieval sermons explaining why they were combining these two stories. It was a symbolic message that would have made sense to medieval peoples, but had been lost over the intervening centuries.
I think it's a trivial observation. For example, it's clear illiterate people in Europe still knew what a cross meant when on a building, there is no doubt about that. There are many more religious symbols that were also well known. Flags and official seals similarly had well known meanings in their own areas, as did various military symbols.
OK, but symbol literacy, at least in this sense, is a long way from literacy in a language having the grammar of the spoken language of these people (or a grammar equally as expressive, as we see, for example, in the case of scholars who read and wrote in Latin while conversing in the vernacular of their time and place.)