One of the things I like about reading "old" science fiction is seeing little bits of history cemented into the story - details, attitudes, and customs that the writer clearly thought were mundane and just "the way everyone did it," but were actually very much a part of the writer's time and place. Examples after the jump.
Heinlein is great for that. Check out his novella Magic, Inc. for descriptions of Main Street small-business culture (and as the true precursor to the Contemporary Fantasy genre) and the small-town characters that pop up in stories like It's Great to Be Back! Or the way the bartender rolls dice with patrons for the price of a drink in a Nevada bar. Or, more darkly, his take on televangelists in If This Goes On and the fragments of The Sound of His Wings...of course the preachers are (unfortunately) still very much a part of our time and place.
And then the nightclubs. Writers from Henry Kuttner to H. Beam Piper to Alfred Bester had the cocktail hour and nightclubs as background entertainment in their stories. And these nightclubs weren't the dance clubs we think of today, but the nightclubs of mid-century, pre-cable America, which provided drinks, dinner, socializing, music, and live entertainment...an entire culture based on adults going out for the evening in their best. (To get an idea of what it was like, check out The Sweet Smell of Success, or the Thin Man movies...or I Love Lucy, for that matter.)
So we could travel to the stars, read the minds of others, imperil the lives of entire sapient races of unbearable cuteness (yeah, Little Fuzzy, I'm looking at you) but the one thing we would never get rid of was the cocktail - even if it was served up by robots. Ah, the way the future was.