Well, let’s say “not in the same house, but just down the street.” Dad was class of 1951, born in the late 1920s.
I eventually found three others at university who could play bridge, but our lunchtime bridge game kind of fell apart after our first year. Nobody else knew how to play.
We never played bridge in college (mid to late’80s), but my roleplaying game club spent many hours in the university union during the day playing spades, hearts, and (most popular) pinochle in between classes. The games would literally run all day, with people swapping out when they had to go to class and then swapping back in when they returned. Evenings were for RPGs and board games, but days were all cards. I loved it. As an introvert, it was the first time in my life when I felt like I had a whole group of friends. I miss it, and would love to start up a weekly card game again, but our local friends (most of whom participated in those college games) are too busy now.
He was probably four or five years older than my dad. So, yeah, same generation, and clearly some similar experiences. 
Remembering farther back to the place we used to spend summers, cards and board games were how we spent the evenings. We only got one channel on the rabbit-ears TV, and most of the programming we got on that one channel (CBC) was not interesting, except for the national news. We had all kinds of reading material and jigsaw and crossword puzzles, but if we wanted to do something as a group, it typically involved cards.
Bridge, as has been mentioned, but also Hearts, double (or triple, or quad) Solitaire, or Rummoli. It seems to be a uniquely Canadian game, and it was a lot of fun:
Sadly, I seem to be one of the few left who ever played it. And nobody I know plays bridge or Hearts or Double/Triple/Quad solitaire any more.
I’m a lifelong model railroader. I’ll be 70 next summer, and I’m the young whippersnapper in my local group. But although the hobby was much bigger in an earlier era, resulting in periodic hand-wringing about the decline, it appears to be back in growth mode.
Bricks and mortar hobby shops have certainly been disappearing, but there is plenty of business on line.
Before I retired, I used a model railroad in my middle school math classroom as a teaching tool, and was pleased to see that the kids found it just as satisfying as I ever did. They just aren’t as exposed to trains in “real life” these days.
My high school had a calligraphy club. How many people do that as a hobby now?
In Japan, quite a few, but I’m pretty sure that wouldn’t be the case in the West.
Japanese kids used to have abacus afterschool classes and I think those have gone away.
I can do calligraphy, but I have not done it in years.
It was discouraging to hear, “It takes you 20 minutes to produce a line? Our new printer can produce a line in 2.6 seconds.” Tech nerds, go figure.
It was doubly discouraging to hear, “Hey can you do a 30-line Shakespearian soliloquy with all flourishes on the letters, with complete illumination and colour on the illustrations?” Yeah, I can do that, and it will cost you $X. “What? You want me to pay you?” the commissioner asked. "It’s like something you do in your spare time, right?
Well, yeah, but unless you’re a really special charity, I’m not doing it for free. Calligraphy is a side gig. You pay me for prettily-rendered letters on diplomas or in Bibles, I happily take your money and render your name in Italic or Gothic or Bookhand where it belongs.
Hey, for an extra charge, I can do it in Baskerville, Caslon, or Goudy; all done by hand.
Yeah, you want an artist to execute a piece of art for you? It ain’t gonna be cheap.
I think hobbies are still popular for young people, they’ve just shifted focus from the traditional to a more evolved version. Cosplay, robotics, 3D printing, that sort of thing.
My uncle (actually, first cousin once removed) used to run a soroban school in the home village, and it was PACKED with kids. I think that was his only job, too. He’s retired now, and I don’t know if the school still exists.
One thing that has happened is the explosion of choices in sports, hobbies and entertainment.
I’m another one from that house! I’m fairly sure that there have been previous threads in which I have echoed your “parents playing bridge” reminiscences. I, too, ended up socializing through RPGs. And still do. Most of my closest friends, to this day, are people that I gamed with in college.
Tabletop roleplaying games, for what its worth, still seem to be going strong. I go to Gen Con every year, and attendance is growing with each con.
Yeah, and people use 3D printing to make complex parts nowadays. Electronics and sound simulation are everywhere. Model railways are very different from when I started.
The answers here are interesting in that everyone is listing hobbies that are popular amongst older generations which may not be being picked up by younger generations. That’s not a demographic crunch, that’s a hobby going out of fashion.
If you think about it most western countries have an increasingly ageing population, so I’d argue that old people hobbies are more prominent than they’ve ever been.
Sorry it does feel like I’m nitpicking, which normally I hate. But it’s okay when I do it… 
A timeless hobby…
I don’t recall many predictions about the death of gardening, but in any case it seems as popular as ever (and given a big boost by people staying at/working from home during the pandemic and having more opportunity to plant and enjoy gardens).
I just returned from a trip where I stopped at a semi-legendary nursery/greenhouse complex (Logee’s, in NE Connecticut), and was probably the oldest customer. There was a gaggle of 20-something Asians making a fuss over their plant purchases. The trend in gardening is likely towards more tub and indoor growing, as property sizes shrink and people are less able to afford homes with enough land for expansive gardens.
I remember (by cracky) when making model cars and airplanes was a big deal among callow youth, and stores restricted purchases of glues/model cement because delinquents were buying it to sniff and get high. Huffing seems to have moved on to aerosol products and of course there are many more drugs to choose from now.
Did you read the OP? That is exactly what the OP is asking.
Same thing at our cabin when I was growing up: lots of board games and card games (including Rummoli), but canasta was the standard in our family instead of bridge.
Yes I guess it is.
In the spirit of that then, how about gardening in allotments or a community garden? I know gardening was talked about just above, but in this case land is put aside for people to grow non-commercial food. In time that land could be lost if demand drops.
As one who got his Private Pilot’s License in 1987 and hasn’t flown as Pilot-in-Command since 1991, I was going to offer flying as a hobby, mostly due to the expense.
But I can’t find statistics that are for purely hobbyists versus those hoping for a future career, so I won’t. The overall number of student pilots seems to be holding somewhat steady.