mamba
Legend
Because the designers would rather include things that most players would actually use, like more subclasses and spells, rather that niche rules that most tables would never use. Books have limited space, you can't include everything.
We are talking about what? a handful of pages? There is easily room for that, they can shave a lot more off by being more concise if they wanted to. The larger font of the new version will take up more pages than this.