It is Sunday morning. That means a lot of people are at church (and who is might be related to the demographic observation you've made). Is the message they're hearing one of hope or despair? Or are they not even listening? I'm not going to blame everything on religion, as tempting as that is, but for a non-trivial minority that might be part of who feels included or excluded and why they react as they do.
Despair. The average age at most churches now seems to be 80+, and those who are younger are there to support their older relatives. There is no chatting or mingling. Once the service is over it is time to begin the process of loading grandma back into the car. What I see of single people at church is the exhaustion common to all caregivers.
What do you attribute this to? Is it mostly just lifestyle choice? Or would most of them prefer to have a wife/gf but don't have one for whatever reason?
Is that true in the enlisted ranks, as well, I wonder? I believe that I saw you mentioned in another comment that you were talking about officers.
Anyway, I can tell you from experience that 20 years ago, around the bases I was stationed at, it was definitely still happening. We went out on the weekends, we partied hard, we hooked up, dated, some of them even got married, etc., with local girls from bars and clubs.
In the 40s, what did a young man have as far as entertainment options? Books, theaters, cigars, racing his motor vehicle with friends, going to horse races, hanging out in bars, finding a public telephone box to call someone, etc.
In the 80s, 40 years later, you had all of the above, as well as basic 8-bit arcade machines (more social because of the high score aspect, going to the arcade with friends etc), then the advent of the IBM PC and cohorts (yes HN I'm skipping the PCs that beat IBM's product to market, hand wave with me please) which enabled computer games with interactive stories and explorations, as well as home media and basic, basic internet connectivity (BBS, Usenet etc.)
40 years later in 2020, we have all of the above plus social media, greater fidelity movies, television shows streamed on demand, the interactivity of the web has made itself available in our pockets in the form of smartphones, smart watches, and tablets, we have virtual reality headsets for even more immersive UX, and all of this is before said social media platforms and app makers started their algorithm iterations in earnest to increase engagement and maximize distraction/user attention time.
In the span of 80 years time we haven't gotten less social by nature, but the sheer amount of engaging dopamine hits we can get from entertainment has gone way up versus ye olde library book or baseball game, so the boredom factor that pushed us to hang out with friends and eventually pair up with someone special is much lessened.
I think even media has evolved to become less useful for meeting people. Of course because of the technology shift from simultaneous viewing/broadcast to on-demand.
Watching movies at the cinema -> you can/want to go with friends. Watching netflix -> you can't watch with anyone except a close partner, because everyone has their own progress point to continue from in whatever series they are watching.
I believe many relationship form after you get to know someone casually over time (classmates, church members) but many people, myself include, stopped going to classes after college and don't go to church.
That leaves at best dating sites but dating sites are super awkward because instead of getting to know someone first, like the examples above, you're instead in a situation where you're supposed to decide yes or no immediately ("do you want to date me?").
uh? by who and why? it's just meme that has various meanings
You probably mean stereotype.