Microsoft hasn't specifically stated that software piracy is the root cause of TechNet's demise. But there's no doubt that a significant number of TechNet subscribers have abused the service. In truth, the program has been rife with petty-level pirating for all of its nearly 20 years.
Back in the early days, packs of TechNet CDs arrived in the mail. It was like manna from the mother ship. And those CDs got passed around.
Today, TechNet's many offerings are simply downloaded as easily copied and shared ISO files. For the most part, the downloads are managed through a sort of honor system. That makes it easy for some subscribers to game the system — i.e., download genuine copies of Microsoft software along with perfectly legitimate keys and then either give the software to family and friends or sell it at the local flea market. Undoubtedly, a few unscrupulous PC resellers sold systems with free TechNet software keys — and charged their customers "discounted" application fees.