This is exactly it.

9/11 was an extraordinary terrorist event: it killed more people than the previous decade of terrorist attacks worldwide. An attack on the scale of 9/11 is simply impossible in the current security climate.

And "ordinary" terrorist attacks are simply too isolated to ever be a realistic threat to any one person. Even in Israel, where terror attacks are commonplace, the number of civilian deaths is very small relative to the population. Or to put it differently, more people died on 9/11 than have died from terrorism in the entire history of the modern state of Israel.

You're more likely to win the lottery while being struck by lightning than you are to be killed by a terrorist.