It is a supply chain where the actors have an atypical participation:
Stock and delivery are generally at one end of the supply chain that has no contact with the final consumer. The intermediary has the indispensable complement in order to complete the provision to its final client.
In B2B2C you can offer your service through another already consolidated company that targets the same consumer segment and over time create a solid B2B.
Although you have to keep in mind that providing the service through a third party slows down your chances of scaling the business, but if you execute it well and with the right alliances, you could scale it well.