Why? Strictly speaking the CD forum is for discussion about the Cambridge diet. Yes, I know you get the occasional off topic post when people forget to post in Chit Chat, but I can't see the point of having duplicate threads all about the same subject.
If each diet forum choose to have a book club sticky there would be loads of unnecessary threads instead of having them altogether where members of this community could talk with each other instead of being in their own little clique. IYKWIM.
For the good of the community it would be lovely for members to move out of their diet forum more often, and get to know the other members here, and having separate off topic threads within each diet discourages that