I usually have the opposite intuition, that centralizing gives greater economies of scale. If a DC could be made more efficient by splitting it into N micro-DCs

I usually have the opposite intuition, that centralizing gives greater economies of scale. If a DC could be made more efficient by splitting it into N micro-DCs, then couldn't AWS just do that? That they do not seems telling. AFAICT centralization offers strictly more freedom in the solution space than if everyone rolls their own micro-DC.