No One Comments

I just got to thinking. Why do most people visit a site or a blog, spend time there, read, watch a trailer, whatever, they never leave a comment.
No one says, hey you stink, so if you do you don't know it. No one says, that was great, so if you were you don't know that either.
Is it fear, maybe, but...no they could go anonymous.
Maybe it's, they don't care.
Maybe no one reads your stuff.
Or could it be that people just think it's too much effort. Just that key stroke or two. What is it?
I make myself do it when I go to most blogs or sites, just because I know how much that person wants me to comment.
Am I nuts? Or do I care and no one else does. Tell me.
Why is it that no one comments.