> It's actually the only one I've ever used, because why would you not?

Because it’s not part of the protobuf specification, not part of a valid protobuf message, and framing is a transport/file format concern and should not be performed by default.

If someone is expecting to receive a protobuf-encoded payload, it must not include a framing header.

> If your implementation doesn't support something in the reference implementation, that seems like your problem, not anyone else's.

Someone else’s failure to follow the spec is not our problem.