They didn't include Clans because nobody used them in Halo 2 and the extra Friend List was worthless?

I even sought help from Deej to push Bungie on the issue. He wasn't interested in pursuing it from TTL Gunslingers. My, how things have come full circle. You'll have to take my word for it because I doubt the exchange exists anymore.

Things like no-Clans in Halo 3 really stick in my craw, forever it seems.

I don't want to support Clans these days but shit, I might have to.

IIRC it was partly due to Microsoft being a bit annoyed internally at how Bungie implemented clans in Halo 2, which from what I remember used the friends list functionality in some way that was a strain on their system.

So on 360, I think the only way clans were going to happen is if Microsoft supplied an OS-level version of the functionality for Halo 3 to hook into. It never came, so 3 and Reach never got clans.

Also for some weird reason, Mattrick era MS literally disliked the term "clans", and at one point Mattrick or someone said they viewed the "everyone adds themselves to a neutral silver account and looks at the Friend of Friends to find other people" as good enough. If you ever saw clans in a game on the 360, the backend had to be invented whole cloth by the developer.