All knowledge is good
According to some, all knowledge is meaningless.
I respond to such threads very rarely but when I do, I do so because I have a background in counseling and because others sometimes offer useless gibberish while the seeker wants some genuine help.
So I suppose I respond for none of the reasons you stated. I don't much desire to help (in the normal sense), nor am I concerned much with others (again, in the normal sense), and receiving ideas from something with the potential to be faulty sets one up for inevitable demise so I don't much read to get ideas. I suppose I read and sometimes reply because in all, it's just what I do.