Not only that, but the answers on Quora seem to be 80% garbage.
But plenty of times I see a question on Quora and it sparks an idea or leads to questions of my own that I then seek answers for independently. It's kind of like browsing Pinboard's "recent" section. Lots of noise but once in a while it gives me the spark I need to find, learn, or create something new.
However, I seek out Quora answers often for questions about people's experiences. I have a long dropdown in my history of searches that start "What is it like..." What is it like to become a parent? What is it like growing up in New York City? Things like I don't know of any better place to find those answers.
I think I've seen an unsourced copy only once, I think it was a new answer where nobody else had seen it yet and I edited in a link to the source. But this is many years ago, I don't remember the situation exactly (and I visit stackexchange sites a lot, more than most people I think, since it's the only social site where I permit myself to go to during work hours).