It's more complicated than that. Reproducible builds help build confidence that your build process isn't compromised.
Sure, your compiler, your hardware, or your distro might be compromised, but if you follow the chain all the way through you does indeed validate version X does result in SHA y, there's now less things were blindly trusting.
It also helps with things like rolling back to earlier versions when you don't still have the binary kicking around without having to revalidate the binary.
If you're not getting the same SHA on different hardware, weeks apart, even if it's good enough for you, it's not reproducible
Sure, your compiler, your hardware, or your distro might be compromised, but if you follow the chain all the way through you does indeed validate version X does result in SHA y, there's now less things were blindly trusting.
It also helps with things like rolling back to earlier versions when you don't still have the binary kicking around without having to revalidate the binary.
If you're not getting the same SHA on different hardware, weeks apart, even if it's good enough for you, it's not reproducible