Unlike with fiat, you're not forced to use any particular crypto. If the rich stakeholders of ethereum decide to muck around with the network, nobody will want to use it anymore and the value will drop.
Demanding a single currency to settle debts is a feature, not a bug. I don't wanna spend each morning researching which currency to use today. And I'm sure the local store doesn't wanna figure out which set of ten optional currencies to sell milk for.
This doesn't even begin to consider long term debt.
