I no longer need to write in any "required style or page format. SO, I never got into using styles. But you have a valid point in needing students to learn how to use it. The fact that writing "style" requirements change every so often. I went to 4 colleges and received 3 degrees. The problem I had was that every time I went back to college, the "standards" for foot notes, indexing, bibilography, and many other things I learn in one college English/Writing course changed. I ended up taking English and Writing courses several time to learn the new standards that the colleges were teaching and required for any paper to be turned into the professors. Then there are those classes that require specific formatting and styles for their paperwork.
If you create a set of styles, one per class/course/teacher, then you can write the documents and then apply the styles needed by the professor, or even the business reader.
I myself have run across times where using styles would work for me, but I never really learned how to use them correctly. Never took the time.
Tom's and other postings about getting students to "compete" in how fast it would be to format a "mangled" text to a predefined style and the others doing it the "hard way". Then having the students "compete" in a race to see who can create a style from scratch for the document. I bet there would be different version created that do the same end results.
The only problem I see with styles is some people may go and make a document so complex with styles for "everything" that it creates problems for an new user to edit/modify the document with new information or reorganize the flow of the document. I had to do that a few months ago and it was not easy. It seemed that every possible portion of the document, i.e. paragraph text and titles, columns and frames, images and headlines, were all defined in such a way that when moving text and images around the document, the styles setup would try to define the wrong text or document element. The editing and moving of text and images broke the very complex styling of the document.
The point is, styles are great in concepts, but some people can get carried away with their complexity. I have a book editor friend that I email back and forth with. She has some real horror stories trying to edit manuscripts that the author wrote using a complex set of styles. So if you teach and/or use styles, kept them simple enough that it does not get in the way of the next person needing to modify the document.