Many times, because there is no direct business relationship between remittance bank A and receiving bank B, it is not very convenient to settle accounts. Just like two people know each other's names, but they are not familiar with them, and they need a third party C recognized by both sides as a transit. This C has business dealings with other banks, so generally, intermediate banks are big banks with strong international settlement ability and strength.

In layman's terms, it's like flying from Shanghai to Switzerland. In many cases, there is no direct route, and you need to choose to transfer once or twice to reach your destination. The middle line plays the role of "transfer".