It does not need to be forgotten. No major event needs to be forgotten. I do think that people need to move on though. If it was the year after I could understand, but it's been 11 whole years since this has happened. I believe we really need to move on. It's terrible that so many people died that day and others lost loved ones. It's terrible that what happened did happen. What we should do is focus on the happiness we shared, all of the wonderful memories we have of those we lost. We should not continuously put ourselves down and fill everyone's hearts with sorrow every single year.
I lost my Aunt when I was very young, even before I was 12 years old. It wasn't something I could have been prepared for either. I was at school when my dad picked me up early. I got into our truck and he said something along the lines of "Mammy's sick, and she's not going to live." When I heard that I immediately started to cry my eyes out. I cried and cried and cried. There in the hospital I couldn't hardly do anything. I just stood and kept silent as I looked at her from time to time, scared and upset. So please understand that I know what it is like to suddenly lose someone that you love.
I wouldn't think that the families who lost loved ones would like to be reminded of the bad every year, nor would they like people to focus so much of their time on talking about the pain and suffering they and others around them went through. They wouldn't want us to give attention to those who committed those horrible acts that day. I personally would want to think only about the happiness I shared with whoever I lost, all of the wonderful memories I have of that person. You don't need a special day to show your respects for those who gave their lives or remind others to do the same. If you want to show respect, do so every single day that you live. Show respect by living your life to the fullest, being happy, and loving one another. Show respect by not putting so much attention on all of the bad things, and instead reminding yourself of all the good.
Reminding people of the pain, suffering, death, and sorrow on that day every single year is completely unnecessary.