Don't get me wrong, but if you want stop it the best way is just to close offtopic, did you ask yourself why admins and moderator tolerate this?
Why admins/moderators doesn't close all these threads straight away then?
Personally I'm person who like to discuss, so if I see some thread interesting to me, and it's open, why I shouldn't post there.
There is a lot of other popular forums which in some way "force" you to post daily, did you ask yourself why?
I don't want to defend spammers but all these what I read here is funny for me. (I mean on that how you describe posts in offtopic)
Anyway good luck to anyone who want stop them.
And yet you are defending spammers with a bunch of fallacies. The existence of shitty topics is not an invitation for you to contribute more shit to this forum. Moderators act when posts get reported to them and usually people don't bother reporting an occasional shitpost but when someone like you starts bumping threads into our watchlists - you will get reported and hopefully banned eventually.
tl;dr: stop looking for excuses to post shit.