Earlier quoted context omitted.
Well from my experience at an American university(though not in the US, so this may not apply). Some professors will assign graded homework problems by simply referencing the page/problem number of problems to solve. If you have a different book or edition then you simply cannot do the exercises. Also, as for requiring the newest edition, it's because bookshops may not have older editions in stock, so you cannot requ…
I think if any lecturers here assigned a problem set from a particular textbook (that the library didn't have enough of) without either photocopying it or putting up pdfs, conscientious students would complain to the students union about the lecturer, others just wouldn't bother doing the assignment. (Actually, in practice, tutors would just give out copies to their own tutorial group). As someone doing a humanities…
I envy the UK system in this regard. But the practical issues of convincing US universities to switch to the UK model are significant.