Like... I obviously wasn't around for it, but...
Growing up everyone seemed to have at least one uncle who was in 'Nam and one grandparent that served in WW2. My earliest memories on newsy things were, like... the Challenger explosion, Haley's comet, Bork hearings, maybe a Reagan speech or two?
But I've met actual adults who weren't born yet when the wall fell in 89 or even when the towers fell 9-11. When it comes to WW2, we had, like... speakers in our schools who were Holocaust survivors telling their stories of the camps. And there's almost nobody who is left from those times, especially with a good memory intact, to tell the stories personally.
It should be obvious that would happen with the passage of time, but it just strikes me as a weird turning point for D-Day to be longer ago than human life expectancy in advanced nations, you know? I dunno... It's one of those "music from my youth is being played at the grocery store" kinda moments.