Forum moderator creates a sticky because they think the thread should remain visible on every visit. For example a welcome thread. You would want all new visitors to the forum to see it but if the thread has not been posted to in a while it will be far down the list and may be missed. Also on Texas forum I have a couple of resource threads about native plants. They are the type of list that people might want to refer back to, so they are stickies so they don't get buried and hard to find.
