Why would someone route their traffic through your servers, opening themselves up to a whole slew of potential privacy issues, and pay you for it, to accomplish the same thing they could do on their own for the cost of a Raspberry pi?
...but neither of those things tell me that you don't still have access to that data, which is kind of the whole issue.
The data is far less valuable than your original claim of "Why would someone route their traffic through your servers" which sounds like a VPN/Proxy.