Why? Because the system's seller wants to, well, sell it you. I.e., the person is out to make a buck. I mean, if the system works, the last thing in the world it's inventor would do is advertise it.
Per this quote from Rishi K. Narang's revealing Inside the Black Box: The Simple Truth About Quantitative Trading
"I'd sell you my kids before I'd sell you my data, and I'm not selling you my kids."
---Anonymous quantitative futures trader