For me, I check the thread whenever there are notifications/add to it occasionally because I am curious to see all of the merch as it's announced, even though I don't like buying merch (I'm nosey).
I think that this is not really a thing meant to be checked through from beginning to end with the hopes of finding something specific (I think most people would probably Google something like "Miku T-shirt" or something if you wanted a specific type of merch, right?). It's more like you want to watch the thread to see what comes out in "real time" and see if said new items pique your interest. (Personally, I watch the thread cause I just like hearing about weird collab merch like Miku glasses cleaner for Father's Day or Miku covid masks and stuff.)
If we had individual threads for every item, I honestly believe it would be crazy/clutter up the forums. Most people wouldn't even comment on each item individually, because I honestly don't think they care unless maybe it was a super beautiful or controversial figure. There are SO MANY items, usually multiple ones, being released every single day. I think this is the first time anyone's actually "double posted" the same item, so it's not like we've had a lot of problems with this merch thread. The only thing I could see getting its own post are the big announcements of like 5+ Crypton figures that are a set or theme something, but definitely not "random overpriced Miku themed bracelet made out of stone beads". ^^;