[zozbot234]

> requiring users to mutate that state through accessors

There are plenty of cases where this makes sense, such as when working with sub-word data (bitfields), which is common in the embedded domain and often found as part of efficient code more generally. In fact, it may be more rare to have actual structs where one definitely wants to provide actual access (e.g. via pointers/refs) to the underlying data, and thus cannot just rely on getters/setters.