If you build the package correctly, you get the exact same binary. This allows users to verify that the binary packages you see were actually gotten by compili

If you build the package correctly, you get the exact same binary. This allows users to verify that the binary packages you see were actually gotten by compiling the source code (presuming your compiler isn't compromised). This means that auditing the source-code is almost as good as auditing the package (the exception being compiler mistakes). Thus, we need less trust in the software packagers.