If you come onto the internet to look at what other people wrote, and don't leave comments or in any way contribute to the conversation, you are losing out on the purpose of being here. Do you see that link... it says "comment" ??? It is there for a reason.
How about on Facebook.... do you read other people's postings without ever clicking "like" or leaving a comment there? Don't you ever think that you're not holding up your part of the conversation?
The internet isn't a spectator sport. It is an exchange of ideas and information.