Part of it might be that the war going on in the middle east and other political/economic stuff is more interesting and heyuri isn't a good place for serious discussions about things like that, part of it could be that most heyurizens are airheads who can't think of anything to post about other than "ZOMG LOOK AT THIS CAT XD" or "POST PICS OF CUTE GIRLS!" when boorus are much better than imageboards for finding pics of cute girls. Someone (not me) should put more effort into making good threads. If you build a good thread, the replies will come.