That’s just how it always is. Most cracks employ techniques similar to virus coding—since they essentially involve reverse-engineering files to bypass game protections. It’s a cat-and-mouse game: a specific version might not trigger antivirus alerts today, but a few weeks later, AV software flags it as a virus. The cracker then has to refine the crack to make it more user-friendly and avoid detection, only for AV companies to flag it again a few weeks later—it’s an endless cycle. I suppose they don't want users pirating the software too much. In fact, some antivirus programs explicitly label these files as "crack" or "tool."