Does it also have a lot to do with the stage of life you are in? In 1969, it was college, and grad school, always around groups of people your own age. When the day was over, you were with groups of people and it was just part of the day to sit around, get high and BS the night away. Also, if I remember correctly..1969 and early 70's, pot was ubiquitous...it was everywhere, couldn't walk around campus without the sweet smell of reefer always in the air.....not so today.
Once that's over, you get a job, married, family, etc...no longer around groups of people, you get home from work, have kids around and other responsibilities....had to sneak down to the basement to get high....no longer a social event...more to just relax.
Once in a rare while, still get together with some old buddies....and it's like old times again...except now we talk of retiring..