Since I graduated and got into the whole "full time job" thing, it's hard to justify pirating a game. However, when I'm not sure if I want to buy something, I'll pirate it to see. Two examples of this kind of game are Dead Space and Splinter Cell Double Agent. The former for the genre, the latter for the bad reviews.
In many senses, I'm a completionist in games. I find every mission and e-mail snippet, I go through and play a pacifist run, etc. But I have not and do not plan to finish either Dead Space or SCDA, because one is "just not my thing" (even when I code in some significant single-player cheat advantages) and the latter is just one of those sequels the fans pretend doesn't exist.
By contrast, Crysis impressed me so much that I now own both it and Crysis: Warhead. (Which impressed me a bit less.)
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If you want to get on a "look at nature" jag... Well, consider immunology. In several cases the body has evolved a system that is a "soft" deterrent, simply because that's the best effort/reward combination. The blood-brain barrier and the corresponding lack of immune response in the brain is one example.
In Adobe's case they've dealt with it by making it work for them. Sure, they'd love it if nobody ever pirated, but if they're going to do it, they've arranged things so that they recoup as much as they can.