[LukeMathWalker]

Agreed. There's also another aspect at play: to build knowledge one step at a time with this learn-by-doing approach, you have to get learners to write code that's not perfectly idiomatic along the way. You then correct and refine those first drafts as you progress along.

In the case of setters, we get rid of them at the end of that chapter by using the newtype pattern thus guaranteeing that field invariants can't be broken even if you can access them directly.