I just found this interesting option when I wandering the "Modify Profile"

I've just googled it and then I found this thread (https://bitcointalk.org/index.php?topic=868974.0)
it turns out that this option is just for Hero Member and above.

This is actually a nice, but I'm just wondering why is it only intended for Hero Member and above? Why not for every rank, or at least for a Full Member?
Is it because Hero Member has spent more time in this place, or for any reason?