Spending money and doing things will always be more fun than earning money. People earn money to spend it on pursuits like rock climbing, even if climbing the rock itself is free, buying the equipment and taking time off to climb it costs money, so those extraordinary things were done thanks to an earlier motivation to make money.
While you're right that making money helps people live an easier life more able to do extraordinary things, climbing culture exemplifies those extraordinary things are possible without it. Much of the development of modern climbing was done with almost no money.
Read Steve Roper's "Camp 4".
Anyhow, most of the climbers I've known were more well to do. It's like ski bums vs. skiers.
There's a great great movie about him that came out a year ago.
Post War America was a time of relative easy living, especially if you were born in America, white, and a man (and were dodging the draft, too!)
However, compared to a lot of other sports that are complex and require a significant amount of equipment, climbing culture is a lot more weary of throwing money at the problem. Critically, a lot of serious climbers are willing to trade more money for more time climbing by selecting less-traditional careers or focusing less on corporate ladder-climbing.
I see it more that adult life is delayed, since there's the opportunity and privilege to delay it. It's kinda rich kids acting like their poor kids, 'cause that's kind of a cool thing to do.
Not everyone of course, but those $100,000 tricked out vans don't pay for themselves. Lots of career folk do roll those out on weekends, but some of those are owned by twenty-somethings. In the minority, you see some people scraping by.
Wut? Not expensive compared to what exactly? You know climbers are leaving material behind in mountains and trips themselves are expensive?
Why would "fit into backpack" be an argument for why something is cheap?
Most of this stuff (aside from the rope) will last for many years. Occasionally I'll lose a cam out climbing which is $50-80 to replace, but only happens a few times a season.
Compare this to skiing or mountain biking and you can see how climbing is a vastly cheaper sport.
Sometimes you have to sling a tree or rock in order to rappel. Sometimes gear gets stuck and you have to move on. Sometimes you drop gear by accident.
Regardless, any leisure time at all is a privilege. Working-class and poor people largely don't have time or money to do _anything_ at all, climbing or otherwise.
I also think you're putting a little too much value on 'adult life'. We can and should work on allowing more people from more diverse socio-economic backgrounds to enjoy more leisure time, not criticize the people that can.
The freewheeling artist/hippy lifestyle of that time period was probably partially encouraged by how strong our economy was. Almost anyone could take the "risk" of dropping out of the workforce for a time to explore their spiritual side.
A white dude in his 30s with a high school diploma in the 70s-80s still had plenty of opportunity to jump into the workforce and start down the road to home ownership and family life.
So no, I don't think it is played out at all.