Interestingly, even small and isolated human groups tend to have very rich oral culture. Why do people "innovate" their story-telling and songs so much faster than their tools?
Because one is a vector for storing information which mutates over time while still preserving.
Physical tools are more complicated, exist as discrete physical instances and knowledge depending upon skill to make it, component availability (needing flint for example), and mutation can occur seperately. Just because you used a partially burnt piece of wood to make a better spear doesn't mean you have the techniques for fire-hardening wooden weapons down.
