That's also a problem, though, because an attacker just needs a large number of nodes to effectively control the currency, which is not challenging or necessari

That's also a problem, though, because an attacker just needs a large number of nodes to effectively control the currency, which is not challenging or necessarily costly (see: Mirai). Doesn't stop the hardware race that leads to centralization. If the incentives promoted by cryptocurrencies inevitably lead to centralization, what's their benefit over the existing financial system?