That's a good question. One of the points I'll make in the follow-up post that I promised is that it is indeed possible to capture the motivation of such an attacker in game theory, and in fact, this has been done. [1] However, it makes the model less elegant and introduces parameters. The more of these complexities you wish to model, the less tractable the model becomes.

[1] http://weis2013.econinfosec.org/papers/KrollDaveyFeltenWEIS2... (Section 5).