Many caves with art in are extremely inaccessible. You need to explain why someone would risk their life and crawl through tiny openings in the pitch black to reach a specific location in order to make their art.
I can not believe that educated people think you can explore and explain human culture without considering "spiritual" stuff.
Assume that prehistoric people drew pictures all over the place, which, given the inclinations of modern humans seems to be true. Then assume that every easily accessible place is likely to have its art erased over overwritten by later humans. Also a reasonable assumption.
What's left? The only ancient cave art we find is the stuff that's highly inaccessible.
In other words, the cave art we see today doesn't reflect the behavior of the original artists as much as it reflects the behavior of later humans that would intercede.
Caves evolve, perhaps there was a landslide that covered old entrance, and that is the only reason why paintings survived. I do not believe paintings would survive in open easily accessible cave. Just the urine from bats...
As for spirituality, people 30k years ago very quite sophisticated. They had paintings, music, maps, religion, porn... But entire population of Europe was like 100k people. And there was no need to crawl into one way death trap, when they had 1000km^2 to explore!
If you’re living in a cave entrance a lifetime of exploration is very different than what we think of as spelunking. Add generations of kids to the mix and little is going to remain unknown and unexplored.
No need for spiritual explanations for something that mundane.
I can not believe that educated people think you can explore and explain human culture without considering "spiritual" stuff.