I don't know.
I don't see a simpler, more laid back time when I look at most of those photos. I see heavy, incorrectly set up bikes, uncomfortable clothing and racism/sexism/ageism.
Concussions waiting to happen without helmets. I would not be smiling in sweaty cotton shorts. Almost all the bikes look like the saddles are too low.
The photos in the first post show one token older guy and one token female, riding a bike in a dress.
The rest are young white guys who look like they may have just graduated from the Hitler youth. I'm sure there wasn't a single black guy, Asian or Latino in America in the 60's.
It's all very disturbing, actually.
Fast forward to 2019. Seems pretty chill.