A lot of it has to do with scale. Stack Overflow currently gets ~7k questions every day. This is actually lower than it was a few years ago when it was more like ~9-11k every day.
The Blender site gets ~50 questions a day. The Emacs site gets ~6 questions a day (with a total of 25k questions in eight and a half years, only about a fortnight of Stack Overflow).
It's just a completely different thing at those scales. It's the difference between a forum with maybe a few hundred people and Twitter.
One of my funniest stories from my time there is how I once closed a question as off-topic (it was) and several years later googled to find one result which was the same question flagged by yours truly (it was still off-topic but the irony wasn't lost).