1. It is harder to see if your crack was successfully completed, especially if the degradation happens late in game.
2. If the game is fun until it goes wonk and the person learns it is pirated, they may decide to buy the real deal.
3. The potential damage, if you didn't have a noticeable false-positive rate, is limited and for those unwittingly hit and find out their software is pirated, they're likely to not buy/get from the downloaded source again.
4. From the standpoint of a developer, it is creative fun.
