Good point. Although we do introduce the long way first.
The reason we don't use a,b = b,a in our code is that it isn't very portable to other languages. We wrote this book as a second semester textbook. So most students are not very good programmers and will be transitioning to something like Java or C++ in the next semester.
Further, for most of the sorting algorithms we have exercises where we suggest that users modify the code themselves to use simultaneous assignment.
Thanks, I enjoy working on all aspects of this project. For anyone interested in helping us out you can find us on github.com/bnmnetp/runestone. I would love to have more contributors.
Thanks for the comments. I'm one of the authors of the book (Miller). Although I wouldn't say that the ADTs are strict ports from Java, I would say that because we teach Java in our next class that was definitely in the back of our heads. Now that we are online, I could definitely see moving in the direction you suggest to make this interesting to a wider audience.