I think that future generations are going to look at this event and be confused as to why it struck our national psyche so very deeply. Don't get me wrong, it was a very, very horrible day. But to consider Katrina for example, while less lethal I think it created quite a bit more overall human suffering. But we moved on from Katrina like we do from most disasters. We didn't move on from 9/11 like that. At some point, you just need to accept that the grieving process is over and move on. Imagine how confused and worried you would be if someone were still grieving their spouse 10 years after the spouse died.
Hopefully I don't sound massively offensive because I don't mean to imply that there is anything wrong with people's reaction to tragedy or the many heroic reactions this event inspired. I just don't understand why everybody, myself included, have spent so long acting as if this tragedy is different from all others.
Edit: What I find very interesting was that a few people were slow to get the memo and treated 9/11 as a 'conventional' tragedy for a few days. I remember my middle school history teacher gave us an interesting lecture in our next class after 9/11 on what it was like in a historical perspective and discussing some of the geopolitical issues that the likely war in Afghanistan would entail. There were some interesting news articles about the attacks that did more then the whole america under siege stuff, actually looking at what we would normally expect. But within a week or so, all of that stuff was gone.