In my experience, the "experiences" that single, underemployed people of working age (20s to 40s) have are largely watching shitloads of Netflix and YouTube.
After all, even if they aren't working a fulltime job, most of their friends are. And even if they find friends who are also underemployed, finances will be tight for both of them, so what exactly can they do together? Usually just hang out at each others' places and watch Netflix and YouTube.
Admittedly this could look a lot different for those with kids, though.
My kids graduated and I moved to SW CO. I have a lot of friends in their early 20s and look at them with the perspective of someone with children that age.
I know a whole lot of ski bums, dirt bag climbers, rafting guides, semi-pro slack liners or whatever. Sound healers and yogis.
To be clear, I'm sure there are plenty of folks watching shitloads of video, but I don't know them because of selection bias. And I know that some of them are trustifarians and others are sociopathic scammers.
Personally, I like my remote coding job. I'm also underemployed but the job is easy and has gentle requirements on me. So I'm a bit removed from what these folks are doing.
However, the folks I know are generally having a much better time than just sitting around watching netflix, and the comment about having experiences taken from us by having full time jobs is a real thing from my position:
being able to just go on a 3 month climbing spree sounds really fun and I know folks doing that, I just don't want to have to re-acquire a job in the aftermath.
Much less so for the underemployed 30 year old making $5k/month off passive income, or a mom&dad stipend, who still has to occasionally look at their bank account.
Pretty common for people in these situations to fall into depression and/or alcoholism.