Nope, that's not it. People aren't worrying about it because it's emotionally costly to worry and the optimal strategy for emotional well-being is ignorance.
While it's true that the consequences of a nuclear apocalypse are much more dire on a global scale, the personal consequences are indistinguishable from a car crash, plane crash or...if we wanted to include a natural disaster, death from a dam failure or a volcanic eruption.
If a typical person worried about every possible way to die today, no matter how minute, that would truly be a miserable experience. Besides, in the case of nuclear apocalypse it is literally impossible to adopt a strategy that minimizes your chances of death in the case it actually occurs, barring moving to the middle of nowhere and digging yourself a deep personal bunker.
So the only reasonable strategy is to ignore it entirely, in which case the likelihood of it happening is irrelevant.