You're ignoring the fact that views::from_big_endian_bytes is less generally applicable than views::from_big_endian.
If I have some structure:
struct message {std::uint16_t message_type;std::array<uint16_t, 5> data;};
Then views::from_big_endian is a good fit for consuming the wire-endian data array, whereas views::from_big_endian_bytes is not.