Because after the killing of Bin Laden, Al Qaeda did not retaliate, which I think is a little strange ? We all know that this isn't the end of Al Qaeda as the organization still exists, so at one point, they should manifest themselves with intentions of vengeance. But what could they do more that the two towers ?
In reality, rather than worrying the attack of AL QAEDA, worrying car accident that may happen tomorrow might be better. America is big and has been thoroughly protecting from the terror. In addition, even if it happens to me, we ought to accept our death occurring suddenly because nobody knows their date of death. No matter how hard we make an effort to prevent it, we can't protect us if it happens. Consequently, not worrying but being positive is absolutely better .
The statistical chance of a person being involved in a terrorist attack in their lifetime is less than their chance of being hit by lightning. It's absolutely absurd how most Americans are terrified of things that will probably never happen, yet cavalier about things that are likely.
Take "stranger danger". We absolutely stuff our kids' heads full about this, shelter them ridiculously, never let them play alone or walk anywhere by themselves. Yet less than 200 children in the entire US are abducted by a stranger every year. Three times as many, 600, DIE playing football each year. The same number are hit by lightning. Thousands die in car accidents, many from texting. Yet it's strangers we're worried about, not letting kids play football or go outside in a lightning storm or drive or have cell phones.