Is there a reason to uses this over something like bazel build?

Is bazel build distributed? distcc lets you use a lot of machines to speed up the wallclock-time of your compilation.

But it has protobufs interfaces (IIRC), so a distributed build farm would generate the grpc endpoints for their implementation and then you tell bazel on the command line (or via .bazelrc) the address of the build farm it can use.

There's a couple of projects that implement the distributed/grpc part, the main one is https://github.com/bazelbuild/bazel-buildfarm