I have to confess that when I know the answer to a question someone is asking online, I purposely don't reply because I like the idea of knowing something others don't.
What makes you like doing that?
Because I want to feel smarter than my peers
I know that feeling.  However, I bet it would feel even better to share that knowledge, because then your peers would know how smart you are!  Knowledge is best shared with those who need to know it!
You really think so?
Yes I do. The next time you're in this type of situation try answering the question. You'll see how great it makes you feel.