Some "required" fields in very commonly used protos ended up being unused, but everybody has to fill them out all the time. If they didn't, the proto wouldn't e

Some "required" fields in very commonly used protos ended up being unused, but everybody has to fill them out all the time. If they didn't, the proto wouldn't even parse, by design. Protobufs explicitly do not have a built-in version system (though of course you could add an optional field for it), presumably because it is better to inspect the data than build in assumptions that a certain version overs a certain invariant.