It can be argued that it's due to thread derailing or whatever but most people have got the sense on who they decide to listen to, so in a lot of cases it seems like the mods are throwing out the baby with the bathwater when they just lock a thread altogether.
Yes, people can read or skip through all the thread derailing posts but why should they have to? When a thread jumps from 5 to 15 pages long, and the vast majority of that is due to several posters fighting back and forth, then it makes it hard to find the quality that is there. At which point, most (if not all) people stop posting anything on topic and it's just the ones fighting their positions, at which point the only thing to do is lock the thread.
What would you suggest is done? Just let threads go off topic and allow people to fight the same battles, over and over and over again, in any topic they feel like it? Make readers have to search for meaningful content? All it does is drive people into Flagpole, I'm one of the ones who only posted in the main forum when I started and now it's completely reversed.
What's happening here is similar to the transfer forum where the crap is restricted to one thread, so people can easily see what is important in the other threads and if they want to see the arguments/random musings then they can visit that single thread. Enforcing the same circular arguments to a single FSG thread or XYZ thread will not end discussion on RAWK. It will just ensure that it's kept in a location where I can choose to read it if I wish, otherwise we still get to write and see the same old rubbish we've always done so in all the other threads.