Frank,
Before ATP, Dave started the "Cubits" site - and I started the Daylily Cubit there. Many of the members of that Cubit came from that "other" site that Dave started years ago. When Dave started ATP, we moved all the posts and info from the Daylily Cubit to ATP, and the tradition of the Porch Swing thread came with it. So, back when I had the Daylily Cubit, we had the Porch Swing for every day chat. It was to keep people from posting get well, happy birthday, announcements of grandchildren, photos of pets etc. in the main daylily forum. Keeping this talk all in one thread.
There is a certain amount of "chit chat" that tends to go on in forums. I think you will find that many of the forums here have a "chat" thread, not just Daylilies. Just from experience, I think it is good to have a place for forum members to casually talk to each other, without starting multiple off topic threads within the forum. There are lots of people who have been members of ATP for a long time who don't even know we have a Sandbox Forum.
It pops up in your new threads because I think it may be the most popular thread on all of ATP.
Quite a while back, we asked the members if they wanted the thread moved to the Sandbox, and the majority wanted us to leave it in the Daylily Forum. Periodically, the older Porch Swing threads are deleted so they do not clutter up the forum.
Technically, the Weather thread is off topic too… but it is something that the members wanted to have within the Daylily Forum.
I hope that helped you to understand….