I understand that the Fanatic and Enthusiast badges can only be attained once, as various questions on the MSO have been asked about it (like this one and this one). However, I haven't found any answer as to why this is the case.
Is it not beneficial to Stack Overflow to incentivize constant traffic, even after the first straight 100 days? It seems as though this would be one more thing which motivates users to keep returning to the website (and, in the process, hopefully providing some quality content or edits), and anything that keeps a website on its users minds is good, sheerly from a business standpoint.
I know there is a general feeling amongst a part of the community that the Fanatic badge is basically just a cheap way of getting a gold badge and should be either removed, demoted, or have modified credentials. However, as a Stack Overflow user, I know that when I was attempting to earn that badge, I would be certain that I wouldn't miss a day of logging in, especially in the last 15-20 days, for fear of losing that streak. And while I was on the page, I'd glance around at anything needing review or questions needing answers, and I'd like to think that I added at least a little value.
I'm not implying, of course, that my own experience is categorical or applies across the board. However, is it truly such a bad thing to add an extra motivator for increased site traffic? If so, why? The only real answer I could think of is that it would somehow devalue having a gold badge, but having multiple, consecutive 100 day periods of logging in would take too long to earn to actually deflate the "badge market" that much.