Maybe for new member captcha enable. I also logged in not using a captcha now. When I first joined this forum I had to type a captcha every time I logged in.
So you are saying you need to be a Legendary account before it's disabled? I seriously I doubt that.
I'm guessing admin is working on to something and maybe he'll drop by here when he's done with it.
Captchas are supposed to be anti-bots and with it gone, the forum would be flooded with bots again.