Consider this for a while longer yourself. Even if many such paintings have been made in easily accessible locations and they do not survive for this reason, the fact remains that more than a few cave paintings have turned up in locations that are very inaccessible and were likely also very inaccessible at the time they were made. The paintings appear to be complex enough that they cannot be discarded as merely graffiti by people who found themselves in an inaccessible location by accident and wanted to leave a mark.

Survivor bias explains why these paintings still exist. It does not explain why they were made.