smartphones and social networks.
My partner's workday ends at 10:30-11:30 pm. I can't get any work done if I don't get up and head to work at ~6:00 am. She works Tuesday -> Sunday. I work Monday -> Friday.
But no, surely it's the fault of smartphones and smooth jazz music.
And while job uncertainty is a give (compared to previous decades) "mismatched job shifts" are not necessarily more...
Something I find fascinating about the pr0n genre is heavily fictionalized fun time is almost any time other than right before or after sleep. But from what I gather of gossip about non-fictional fun time, most "settled down" couples stick exclusively to immediately before or after sleep, which is kinda weird. I can assure you all the parts work fine if you meet up at lunch time or pretty much whatever you're physically together, you don't need permission from a wall clock to have a good time.
they grew up having less distractions to spend their time/energy on, even TV wasn't part of daily routine. So once all the talking is done and there is still time to kill... I remember reading about 20 years ago about India plans to produce cheap national TV sets to help combat high population growth, i.e. to give people something to kill time with other than the activity which naturally results in new children.
That "more single people" is basically a restatement of the phenomenon of less sex, and not an explanation.
Instead, this thread is full of speculation akin to the most click-baity of science journalism: relatively boring paper goes in, crazy theories come out.