By any measure, the summer of ’69 was , as the kids say today, “a lot.”

June had the Stonewall riots, a landmark moment in the modern gay rights movement. July, the moon landing. August, the grisly Manson murders, followed by the endless mud of Woodstock.

These events have been fodder for countless songs, movies, university courses, history books and romance novels. And now, in 2019, they have begot another special summer: of 50th-anniversary celebrations that are public, elaborate and full of nostalgia. Millions of people from around the world are joining in, along with sneaker designers, toothbrush companies, hotels, museums and news organizations.

Far be it for us to deflate the spirits of those, say, dancing in constellation-printed rompers and drinking Budweiser at the Space Center Houston a couple of weeks ago. But then to happen upon less momentous commemorations, like a copy of People magazine celebrating the 30th anniversary of the movie “When Harry Met Sally” at the corner newsstand, is to wonder: Just what is the point of marking them? Is doing so essential somehow for society’s psychological well-being, an attempt to collectivize experience increasingly diffused by the distractions of the internet? Or just more chances for corporations to sell us stuff?