It's crazy how much money people end up spending on these kinds of things. A hundred here, a hundred there, before you know it you've spent tens of thousands, maybe even hundreds of thousands. Most probably don't even realize they're spending that much.
From someone who has been part of the hobby for a long time, I think a couple of reasons:
1) Total Warhammer, Space Marine, and an otherwise highly successful video game licensing program.
2) Being well positioned to ride the overall rise of nerdier hobbies being acceptable
3) A marked shift in the company towards being more open and...friendly? It's hard to overstate how much the "old GW" sort of viewed its customers with a vibe that sometimes came close to hostility. There's much better engagement now, and a business built on something other than "A mom will buy this for their 12 year old, and will lose them when they discover girls."
I think the image of 12 year old boys as GW's customer base is probably outdated. I know a woman who is _massively_ into Warhammer, and spends a lot of money and time on it. An N=1 anecdote is not data, but it would certainly be interesting to look in more detail at GW's demographic.
For some applications, PLA is a little more rigid. It will then fail in a spectacular fashion, but "I need you not to bend" is something PETG doesn't always perform the best for.
I don't do this because I don't have the time to design wargaming terrain, but I've definitely pushed myself to do more designing for household things.
It's a really good feeling to be able to put something together that solves your problem. As I asked my wife, "Is this why people with wood shops are always so smug?"
It's also fun to be able to feel your skills building. I now have opinions on friction fit box lids.
There are places where 3d printing has revolutionized the wargaming hobby. Terrain is one of them, and the biggest one I think. And there's games like Trench Crusade that got their launch via being 3d printable, allowing them the critical mass to get to plastic production.
But at the end of the day, if something is in plastic, I'm buying it in plastic. And I am disappointed by the amount of energy and talent not going into creating new things but...Legally Distinct Space Marines, often sculpted with no notion of actually ever being painted (way over-detailed, etc.)