you need different packed structs for little- and big-endian data. and casting with little-endian data is a nightmare - you need to reverse-cascade your struct fields to be in accordance with the little-endian bit-pattern. (or have a comptime function that does it for you, of course. but then you lose all declarations for the struct). what should be a simple writing down of a protocol is now a pedantic and error-prone ordeal.

This has been largely solved by everyone agreeing to use little endian. There aren't really use cases for wanting to convert between them.