Kent is correct.
Rick Steves' guidebooks are not comprehensive guides, they cater to North American audiences who go to a country for the first time, therefore he covers only some of the top sights that can be visited in a couple of weeks. So he makes a selection of those top sights based on what he interprets that could be of interest to a North American. Turin, I guess, doesn't make his cut, not because it's an ugly city, but simply because in the list of top sights that can be covered in 2 or 3 weeks in Italy, there are other sights that should be visited first, at least in his opinion.
I don't know Turin myself, I've only passed through it a couple of times, in spite of having a lot of family in Turin (or maybe that is the reason :). However if you have visited Italy before, and want to venture beyond what RS covers in his guidebooks, in other words if you are an "advanced student" and not just a "beginner student" of Italy, then you should upgrade to parts of Italy that are not covered by his guides. Some of the areas that he totally ignores are, in my opinion, even better than some of what he includes in his guides, so that tells you that we all have different opinions. For example I prefer lake Maggiore and lake Garda to Lake Como, but for some reason RS likes lake Como better, maybe because Varenna is so easily accessible by train from Milan, while lake Garda is better if you have a car.
If you would like to venture into Piedmont, I recommend Lake Maggiore, Lake Orta, and the wine producing regions of Langhe and Monferrato. If you like mountains and ski areas, Limone, Bardonecchia and Sestriere are top locations (the latter two were venues during the 2006 Winter Olympics).