It depends on the target language. I think the driving force behind the protobuf3 simplifications were to make working with Go better. Go pretty much required dropping the 'required' and non-zero-value defaults. Which annoys Python developers and similar with access to a None, nil or NULL value. It is particularly visible on my main code base, where I'm dealing with SQL with NULL, to a Go gRPC server which needs specially handle all those NULLable columns, via protobufv3 to Python clients which generally now can't tell if the original data was an empty string or NULL (because the solution to that is worse than the problem, which is annoying but manageable). protobuf3 is designed to be cross language, which in this case meant going to the lowest common denominator rather than making it work harder.

Yes, I would love if there were set/unset bits available. Even if it was awkward.