History of American law school, and Canadian because Canada follows America's lead more than Britain's. Every other nation/legal system has law textbooks, what are called hornbooks in American law schools as primary texts. The idea that the law can actually be reasoned about socratically is... strange. Precedent and path dependence are huge parts of the law. And the law doesn't change quickly. If you read a UK law textbook there will be references aplenty to cases from the 1800s, more from more recent times but the law is actually remarkably stable.

Harvard's case system didn't spread because it was better as a method of legal education, it spread because one of the most prestigious college in North America started using it and it's more fun to teach that way. The Socratic method has a place as a method in teaching but having it be the method is overkill.