The main benefit you'll hear touted is something along the lines of being able to get an attestation that the resulting artifact was built following the steps c

The main benefit you'll hear touted is something along the lines of being able to get an attestation that the resulting artifact was built following the steps claimed to build it. I think that's a somewhat overstated benefit, though, as it's not clear to me that this is an avenue of attack used in practice, given the frequency with which software already has vulnerabilities usable for exploits, or the ease with which one can insert a backdoor into the source code (e.g., the xz backdoor). I think the actual main utility is that the process has done a very good job of rooting out several causes of unintentional nondeterminism in the build process. I say unintentional because the two main causes of unreproducibility, by several orders of magnitude, are timestamps being embedded everywhere and absolute paths being embedded everywhere, and those are rather expected. But some of the unreproducibility comes from things like accidental reliance on inodes in file paths (i.e., doing "for file in listdir()" without sorting the results of listdir) or the compiler itself accidentally sorting based on pointer address (which is unreproducible on ASLR systems).