User blog comment:ISharkyShark/Trading: Assumption of why it was added in 1.0.4/@comment-31479721-20170331171949

I think it's because it didn't really fit with the theme of 1.1, and there wasn't a good major update to have it in, it wouldn't fit with the theme ever, and like you said, trading was necessary for the Cartographer, so they couldn't add it in later. That's my theory.