I think there is a key reason as to why the final "day before" 9/11 doesn't stick in our minds as much as the day before Pearl Harbor does in our parents' and grandparents' minds: Because Pearl Harbor directly altered their personal lives forever. After 12/7/1941, the parents' sons were sent off to war. Many husbands went off to Europe and the Pacific as well, while the wives ended up working in offices and factories for the first time in their lives. There was rationing. Friends and family came home in pine boxes on a regular basis. Their day-to-day lives were turned upside down for four years after Pearl Harbor, and the majority of the American public had the overall courses of their lives changed forever. (I wouldn't even exist today if it weren't for WWII; my mother's parents met at a USO dance in the early 40s.)
After 9/11, however, for the vast majority of us, our own personal lives did not change at all. Remember when Bush gave his first big post-9/11 speech and his main instructions to the American people were "live your lives"? And how so many people compared that order to, in effect, do nothing, to the sacrifices Americans had to make during WWII?
That's pretty much what happened. Our political viewpoints may have hardened (or swung around 180 degrees in some cases), our fears of "what's out there" may be different now, but unless you or an immediate family member are in the Armed Forces, or you worked or lived in Lower Manhattan, your day-to-day existence is probably not one iota different now than it would have been had 9/11 never happened. (Yes, I know some people could make tortured arguments about how "the post-9/11 financial hit caused me to lose my job" or something like that, but proving a direct connection between the two events would be impossible in almost all such cases.)
I know my life is exactly the same now as it would have been without 9/11. Which is why I can't remember any specific events that occurred on 9/10. I suppose if I'd attended some great concert that night, gotten married, had a car accident, or some other event that I would inevitably have remembered anyway (none of which happened; it was just a regular generic day for me), I'd think of that occurrence in terms along the lines of "Oh yeah, that was the day before 9/11!" But would I think of it in terms of "the last day of the Old America," or "the day before Everything Changed"? No. Because nothing has really changed for most of us. Our feelings and opinions were altered by 9/11. Our EXISTENCES were not.