About half of the first page of
Anime and Manga is full of locked threads, and next to none of them have been posted in by whoever's locking them to give a reason as to why. When you don't give a reason, people won't get the message as to
why they're getting locked, so people just continue making those threads.
One thing I've learned in my time in retail is that people don't read things properly or even at all, and I'm no exception to this rule. So the sticky at the top of the forum informing users of the rule might as well not exist. I'd recommend just being a little more direct with a user by giving a reason and directing them to the thread that states request threads for unlicensed content isn't allowed, even if it's just a simple copy-paste like this so they can figure out the reason for the lock on their own;
I think that would eventually hammer in the message.
Due to the sheer number of locked threads as well, it might be prudent to purge some of the older ones just to clear the section up a bit.