I also own the book, but as I have written to @muscara, have not read it completely (only some chapters, no idea why I stopped) I think the book focuses on crafts like knitting or crochet because they have a repetitive and rhythmic character. And that you can achieve nice results without exercising for a long period of time (like for playing an instrument) and that you can do it exactly like you described, in short bursts of time (not so easy for a fast-drying acrylic painting).
But nevertheless, you are absolutely right: every creative activity can facilitate health or help to cope with stress and physical and emotional pain. As every person is different and prefers different artforms/hobbies, it is good there are so many wonderful techniques...