Note that I didn't just adopt the build system to build container images. There are also lots of other build steps that I wanted to do (compile Protobuf & gRPC

Note that I didn't just adopt the build system to build container images. There are also lots of other build steps that I wanted to do (compile Protobuf & gRPC definitions, build a frontend web application and build it into the binary, etc.). If I already want to do stuff like that and Bazel does that well for me, then at least in my case there was no incentive to use any of the tools you listed.