For better or for worse, 9/11 is slipping into history and out of present day consciousness. Had to remind friends of mine originally from NY that they were flying to NY on 9/11 so expect delays. They had completely forgotten when booking, and even when I reminded them dismissed it as nothing of concern.
In many respects, Bieber stripping on a TV show has more impact on the consciousness of Americans than what happened on 9/11 13 years ago. I guess it's natural. Time marches on, even though the threats from the same enemy are still very real today. In a few more years, 9/11 will be remembered similarly to 12/7. Something for academics, military types, history buffs and older people to commemorate while the emotional impact on most Americans becomes negligible.
Days like 12/7 and 9/11 may indeed live in infamy, but in reality they tend to fade as the generations directly impacted gray and whither away.