One of my earliest memories (I'm told we moved from that house in 1970, so I was 5 or less) was a demolition derdy model kit I got for Easter. I modeled steadily from then on, mostly whatever Monogram 1/48 WWII AC the local 5 and 10 had on the shelf. A treat would be to go to the good LHS for Pactra paints and possibly an Aurora kit if I had two weeks mower money saved.
Most of my birthday and Xmas gifts until I was in 7th grade were models, the 1/48 B-52 and B-17 stand out in my memory.
All were built at a card table in my room, an X-acto, file and Testors orange tube glue. I'd start off vowing to carefullt cut and file each part, but eventually blew through that and slapped 'em together.
Gave up when I started playing bass and discovered girls. Or more accurately discovered girls, then started playing bass so I could land said girls.
Flash forward a solid 20+ years, shopping at a train store for my son's Xmas present and at the register they had a bunch of 1/72 DML RC Tiger Is. It brought me back to kiddom, Saturday afternoons of listening to Olivier narrate World At War. Even though it was pricey, around $70, I couldn't pass it up. That was the coolest present that year, we played with it for hours.
I was jonesin' for modeling then and I thought it was out of the question, since I couldn't be around most solvents (had a spinal cord tumor), but looked into it and found a whole new world of acrylic paints, non-toxic glues, etc. So I eventually grabbed a Revell 1/72 Pz IV and did most of the assembly under the kitch exhaust hood. Hook fully implanted, I was done.
Moved onto a 1/35 Tamiya Tiger I RC with Aber, holy cow has the industry changed since I was a kid. Got on the FSM forum to research and made a lot of online friends. I was finishing my attic as a playroom for my kids, so I sectioned off a 9 foot section for myself, installed an exhaust fan for a spray booth and never looked back. Even started a small business around it.
Onto your second point, I'm not sure if it's the nature of the hobby or that many in it have similar back stories (build as a kid, rediscover as an adult with kids), but it is a perfect online/forum hobby.
It's easy to share with photos, has wide interests and truly opens up what is a solitary hobby.
I've been a member of a few different forums, for bass, RC stuff as well as came across a bunch when needing an answer for car/home repair, etc, but have to say scale modeling as a rule seems to be the most community oriented. I can honestly say I've developed friendships across the globe, even though I've never met these people face to face. My kids have received prehistoric shark teeth from Cape Town, Harry Potter stuff from the UK and postcards from the northernmost PO in the world all from thoughful modelers.
Think about it, how many online forums have Secret Santas beside modeling. I'm sure there are somewhere, but none I've ever seen.
Every time I click on a thread, I'm inspired to try something else.