Porn discourages discussion and encourages normalfag degeneracy. Look at 4/b/. Nothing but porn threads and generals. Even other chans are not safe from this curse (cripplechan /b/ has now banned them and limited them to one thread at any time for porn dumping). Many sites I know maintain a septate image dumping board to contain porn threads.
Probably why the mods of India chan banned porn from its inception.