A Lives in Sri Lanka, B lives in Rwanda. They know each other. A would like to employ B to assist with the writing and testing of some software. A would like to wire B the payment upon completion of the service.
A goes to the bank to deposit Sri Lankan Rupees, in to Bs account. B must find a bank willing to accept foreign currency and then convert the rupees in to francs. The bank charges a fee, the bank also charges a fee for FX. A and B would like to do this regularly such that B gets a share of when the software is sold. This software gets sold quit a bit. A&B have a great business, but they realise its a 3-some as the banks get a slice of the action.
A decides to use a digital currency. B does the work, A pays... A can automate the payment for the future royalty. A & B are happy, the banks less so.
the problem you are describing there is an inefficient or costly banking system.
Using online banking, I can transmit money securely to your bank account without charge.
If you are in a foreign country, and your country has decided to cut commercial links with mine, and not to use a common means of exchange, and to allow profiteering, there may be inefficiencies and costs.