I think when you still have a few/several stone to lose, SS is quite an attractive option for some people because you don't have to make any choices about food at all, and for many of us it's making choices which has been the root of the failure of the diets we've tried before. If you can make choices you can bend the rules, whereas there's no scope for bending the rules on SS at all. It's a relief not to think about food.
SS+ works really well, and is the best option for people who find giving up food completely to be hard and undesirable. But other people don't feel like that, and for them there is absolutely nothing wrong with SSing until week 13 / target. Provided they go up the steps they can deal with real food at the end of the journey, when they no longer have months of diet stretching ahead of them.
Lastly, CDCs vary in quality and ability, and even the good ones don't know your body or your mind as well as you do.