decentralization is not the utilitarian value of Bitcoin, it's a side-effect of its utility, though. No, the utilitarian value of Bitcoin is in everyone having enough to support a market for goods and services (we'll ignore legality of any particular good or service for the moment, but that is important as well). Their value is in if there are people willing to take them for goods and services. If neither condition exists, it doesn't matter if they are decentralized or not, they completely lose their utility and hence, their value.