The fact is they never do, they are too lazy! When I could still edit thread titles, I went to many old ones, checked that the translation was done and added [COMPLETE] to the title. Because new subbers kept writing on those threads (which came as search results) and they didn’t think of looking at the date, which in some cases was as old as 2016 or 2017!
On the other hand, there are some old, semi-abandoned projects, which still need subbers, even after many months.
And we can’t keep making the rounds and reviving all the old threads once a week, that’s too much work!
And they destroy Chinese shows by stripping the HONORIFICS OFF. Not exactly helpful as that is one way to tell who knows who and to what degree. Sigh. Formality matters, who is courteous and why. It is part of the plot…like in a historical or costume drama, the pictures of the shoes…footwear determines status often and who you are.