Jolie and SODEP predate grpc, so we don't have grpc just because we had no need for it (we already had a binary protocol with expressive interfaces).

It's definitely something we'll get around doing sooner or later though, since so many people use it, and we do care about interoperability. Contributions towards this would certainly be welcomed warmly.

PS: We support integration with Java, so you hack your way around this by using some Java code for grpc, but it doesn't feel "native" and require some boilerplate.