I suspect that may be because: a) The game wasn't big enough in pirate-space to garner the interest in a pirated copy. b) You just haven't seen the pirated copy.
This stuff actually makes me quite angry, the developers and the customers both suffer, the only ones that don't are the pirates. It's quite easy to boycott the game or get your "drm free version" but the studio and devs who have worked hard on an otherwise good game are the ones that suffer. Also to those who say steam is…
I'm not really understanding the concept behind this though. Piracy, not game rentals or friends borrowing copies is what the industry is worried about and what ultimately costs the most sales. But this won't stop piracy in the least. What's the idea? That once the pirate installs the game anyone with a different card…