Also Ecuador uses the USD, with a GDP of ~$100bn. There's a big difference between having a currency pegged to another, and not actually having a currency at a

Also Ecuador uses the USD, with a GDP of ~$100bn. There's a big difference between having a currency pegged to another, and not actually having a currency at all, and using physical foreign currency for everyday transactions. Pegs can be broken and may be hedged with FX futures. The second situation is a much stronger existential commitment, which makes it more reliable and predictable. Reinventing a new national currency is a high barrier, which cannot be hedged directly in the FX markets (although sovereign CDS might be close enough).