I get good answers all the time on SO or used to. My problem is that I've been down voted several times for "stupid question" and also been down voted for not knowing what I was talking about in an area I'm an expert in.
I had one question that was a bit odd and went against testing dogma that I had a friend post. He pulled it 30 minutes later as he was already down 30 votes. It was a thing that's not best practice in most cases but also in certain situations the only way to do it. Like when you're testing apis you don't control.
In some sections people also want textbook or better quality answers from random strangers on the internet.
The final part is that you at least used to have to build up a lot of karma to be able to post effectively or at all in some sections or be seen. Which is very catch 22.
So it can be both very useful and very sh*t.