It's an easy fix if Google cared. Have an online tool that validates if the robots.txt is correct, and send out an announcement that files that don't meet spec will be penalized in terms of SEO.
https://qph.fs.quoracdn.net/main-qimg-002d1f819e1bfbbd14fa2d... shows some of the interface, but I seem to recall getting notified in webmaster tools when I messed up the robots.txt on a particular site.