That's true, but I think that it is due to a few factors: JNI is considered a big penalty in the java, and treated as a "last resort" (libvips is an example); g

That's true, but I think that it is due to a few factors: JNI is considered a big penalty in the java, and treated as a "last resort" (libvips is an example); go community has been advocating against C bindings since the runtime was itself rewritten, and treated as an antipattern; protobuf and grpc teams are compromised of mostly googlers, which have more incentives to optimize java and go (it's known that a big chunk of their services are java and c++, and most new stuff is go). And the rest might as well just use the bindings, as it's probably easier to maintain for them, and low in ggwir priorities lidt. There's actually a pure ruby protobuf library (I believe square employees use and maintain it), but it probably won't ever be merged into google/protobuf for those reasons.