But, ultimately, if there are legions of people able to bowl or curl or play softball once or twice a week with stable teams even though they're married with kids and employed, it's not that hard to imagine doing the same with gaming.
Well, here's the thing - leagues and D&D games are typically different, along the lines of what I said earlier - you get the team you want, or the schedule you want, but not both.
In a league, the schedule is set before any teams are made - team captains then go around to people they know, and assemble a team out of folks who are
pre-selected to make the schedule. Some of his preferred people probably aren't available, and so won't be on the team this time around.
Also, in my experience, league play is usually weekday, and as I understand it, folks tend to play in very local leagues, not ones that are 45 minutes or more drive away. Leagues tend to be seasonal, not year-round commitments. Leagues always have rules about attendance, and have forfeits if people don't show up....
Yes, I could put a game together, if I were willing to build it like a league team - take my group from a large pool of players, and be willing to tell anyone who could not fit my pre-determined schedule that they're out of luck. Some game, with some people, could be assembled, surely. It would eventually collapse to have people traded out and new folks traded in, as seasons and life-changes altered individual needs. That is typical of league play.
But that's not my situation. I don't want to choose the schedule first, and then pick people to fit. I've got a set small group of players I want to work with, that I've been playing with for 15 years, since everyone was a student and had more free time than sense

If I want to be that picky, my preferred schedule is probably forfeit.