If you add enough intermediaries in any transaction, you efficiently make it opaque for both parties involved. Two factors play a role: human laziness and corporate confidentiality rules. While both parties to a transaction are usually entitled to ask for information about their respective partners as a form of guarantee, confidentiality rules usually limit such information to the direct partners. And most people don't have the time or don't want to make the effort to look any further and gather the proper intelligence. Especially when a high number of (relatively) small transaction occurs frequently, it becomes impossible to check more than a couple of them at any time.