I’ll give you one example where the protobuf design helped out a lot: GWT Protobuffers. The GWT Compiler has a version of Protobufs that transpiles all of the protos into Overlay types of naked JSON objects.

You get a statically typed Java interface, but underneath it a raw JSON object, and deserializing the proto is basically JSON.parse() + a cast.

e.g. something like this

MyProto foo = MessageDeserializer.deserialize(serializedProto); console.log(foo.getFieldFoo());

compiles to this JS:

var foo = JSON.parse(serializedProto); console.log(foo[1]);