The bottom line is that it doesn't matter how I feel about it. What matters is whether or not it works. No, it does not accomplish anything significant that I have seen.
Sub for sub seems to be a practice which is just perpetuated by a continuous stream of new users. They visit this forum for the first time, they copy the threads that they see, then maybe they grow frustrated or depressed when thia specific form of self promotion does not create the snowball effect they wanted, and lastly they quit creating or exit Tapas and leave behind a forum post which entraps the next user. If this forum had more active admins, the process might have been stomped out by now.
Now maybe I'm wrong. Maybe you only care about the stat instead of an actual readership. Maybe your goal is humble enough that a small community of your fellow creators and no non-creator readers will satisfy you. Maybe you love to self-promote here exclusively, and I'm full it. M'okay, there are dedicated and pinned official threads for self-promotion-- and none of them are share for share threads.