Because AutoCAD 2013 sits at a fascinating historical intersection. It was the last version that felt "brute-forceable." Later versions moved to a more aggressive, always-online licensing model (the "Product License Activation" system), making X-Force-style keygens virtually extinct. The 2013 version, however, was the bridge between the physical DVD era and the cloud subscription hellscape.
Using X-Force on AutoCAD 2013 was a strange act of rebellion. It allowed a broke student in a dorm room to learn 3D modeling and parametric constraints on a $4,000 piece of software. That student grew up to be a professional who now buys the license for their firm.
Mention "AutoCAD 2013" today, and most professionals think of the Ribbon interface’s maturation or the introduction of cloud connectivity. But in the darker, quieter corners of the internet—forums like CrackzPlanet and The Pirate Bay —AutoCAD 2013 was inseparable from a small, 2MB executable bearing the iconic skull-and-gear logo.