A co-creator of the original Fallout has said the classic RPG was "entirely different" from foundational role-playing games such as Ultima, because those earlier titles were built on the assumption that players would act as good, moral characters. Fallout, by contrast, was designed with no such assumption, allowing players far greater freedom to behave selfishly, ruthlessly or outright villainously without the game pushing back against that choice. The comments highlight a deliberate design philosophy that helped set Fallout apart from the RPGs that preceded it and shaped the morally flexible, consequence-driven style the series became known for.

According to the co-creator, older RPGs like Ultima were built around an inherent expectation of heroism, with players cast as virtuous protagonists navigating clearly defined moral frameworks. Fallout's designers instead removed that baked-in expectation, giving players the latitude to make selfish or morally grey decisions as a core part of the experience rather than an exception to it. This approach is credited with giving the post-apocalyptic series its distinctive tone and its reputation for reactive, player-driven storytelling.