Well, if the hacker want's to keep hacking, they can just either move their thread, or have it be dumped, and continue on working, then when they have enough to get into "Progressing Hacks" then the can post a new thread there.
The thing is, the scrapbox ha turned into a dump, and that minuscule amount of hacks that actually mean something, can just be continued without a thread. Then when it is good enough for progressing hacks, they post it there.
(You don't need a thread to hack)
It can be like a test, to see if the people in the scrapbox actually care enough to keep hacking, or if their thread was going to turn out into junk in the end.