I think the main thing is that in order for a retrospective to occur, such that a historical perspective or even nostalgia is gained, there has to be a culture identity clash. For example, by the time of the 1970's the 1950's seemed like two worlds ago, for all that had happened to change the identity of the culture, thereby creating a perspective wherein a nostalgia developed naturally, in no small part due to George Lucas, who's "American Graffiti" was really the 1st to start the practice of using the 50's as a set for a period piece, spawning a decade of popularity for the genre, with Happy Days, Grease, American Hot Wax, Sha Na Na etc...
The period in which the 60's were used & looked upon similarly, but never as popularly, was during the 80's & 90's, when bands like Phish, Blues Traveler, & Spin Doctors were in a rift of Retro-Hippie, & during which the following for The Grateful Dead bloomed rather profoundly
That period is long gone, & therefore the 60's like the 50's is just another in the long history of periods in U.S. culture from which to ponder its distinctness, a distinction which is usually founded in how those who lived through the period look back on their youth, & how the younger generation begins identifying them with it
The reverence for the 70's has since passed as well, during the 90's, in the form of Neil Young sharing the stage with Eddie Vedder & Pearl Jam, & that whole grunge era being a somewhat retro movement. Finally, we are now still in a nostalgia for the 80's, with Gaga being our new Madonna, & a resurgence of popularity for the music of the late Michael Jackson, who in death has escaped the stigma of alleged pedophilia. Every Republican politician touting the historical greatness of the Reagan era, which actually managed to manifest itself into a 21st century Bush legacy
I now remain curious to see how this culture will ever manage to memorialize the 90's era, which was predominantly inhabited by Gen-X, known primarily for its lack of identity, & being consumed by frivolous nonsense like Lewinsky scandals & the O.J. trial
Sadly, I already have an idea of how history will view this current millennial era. A digital landscape of technological development, with social & cultural turmoil. An American populace so watered down & ignorant that the most news worthy social movement that occupies Wall Street, has absolutely no focus whatsoever, in a time where liberty is being stripped & trodden upon, for the sake of security, & people are either too stupid or hopeless to bother to do anything effective about it, & journalism has been replaced by reality tv
Make no mistake. We are shaping history right now, & it's shaping up like complete shit. Sorry to be such a downer/pessimist, but there you have it