At least Rust has far less building systems than C and C++ building system jungle: C, GNU Make, BSD Make, Windows Make, GNU autotools, and much more. Google may have a valid reason for not using Cargo, since they may need to integrate Rust with existing C and C++ code. It would be nice if Cargo had a way to build and link C and C++ dependencies in the same source tree as there are many C libraries which the functionality is still missing in Rust.