Even if the information asymmetries across the medium of exchange are close to zero (as it is expected in a decentralized financial system), there exists a trust imbalance. And there are different levels of trust among trustful parties: naturally, a merchant will trust a local broker more than its foreign counterparty. In the middle, there is no need to trust a bank, a correspondent bank, or even a government. You just need to trust that people will pursue their own self-interest: miners will verify transactions while it is profitable to do so, and over-the-counter exchanges will maintain order books as long as there is demand. There is only the issue of on-ramping and off-ramping to fiat, but one could argue that this lies at the boundaries of the medium of exchange -- it is a trust coupling problem. Therefore, whoever can level-up trust provides a valuable financial intermediation service — at least until the system becomes mature.