Inequality as a driver of innovation is maybe arguable based on the idea of risk/reward. But what about, for example the CEO of any large bank or established corporation. Those people aren't taking any significant risk, but their compensation packages would indicate otherwise. The organization that concentrates wealth towards the top is already in place. They profit from the success of that organization, but in most cases the worst case for them if things go wrong is losing their job. Not losing their life savings, not ending up living on the street, etc. So since the risk is so low, there shouldn't be a need to incentivize people to such an extreme to do that work.