Different people learn in different ways. There are lots of people - me included - who don't learn well from books or online tutorials. We need to be immersed in the environment. We want to be able to ask questions and get human responses. The Starter League is especially well suited people like this.

in a perfect world, everyone can learn from books. i know that my learning style is MUCH more interactive and i only really learn in a classroom setting. Having done the spring dev course for Starter League (then codeacademy) I can tell you how amazing it is to have material presented, then challenges with pair programming right in class. TAs walk around and help you when you get stuck, thereby teaching you how to deal with error messages. learning from a book can be such an isolating experience, whereas classes are much more about community.

One of the ways I (and I suspect others) learn best is by asking questions. This is the primary downside of an online only course.