Topics that require very little thought for any noticeable reaction attract more people. See /dqn/. The effort needed to participate on 4-ch is truly minimal, but the contributing audience is generally desensitised to trolling, which, while helpful in keeping discussions mature, also hampers their ability to veer into more interesting and controversial digressions.
The form of trolling that receives most responses here are regurgitations of stolen net memes that have long since lost their impact, which further deteriorates the perceived quality of our openness to new contributors. "Anonymous does not forgive" and other hostile in-jokes of that manner effectively repulse many people who might otherwise consider spending more time here.