Protobufs do require more effort in the toolchain. Pretty much the only way to parse a .proto file is with protoc and you might need to build it from source. So you need to run the C++ compiler and depending in the build system you're using, adding a dependency on protoc at build time can be a pain.

Contrast with JSON where every decent language ecosystem has a parser readily available. That's what makes it the "gold standard" for me.