It was used as a source of randomness. Someone blindly fixing a "bug" as reported by a linter famously resulted in a major vulnerability in Debian: https://www.debian.org/security/2008/dsa-1571
If they had simply removed the offending line (or, indeed, set a preprocessor flag that was provided explicitly for that purpose) it would have been fine. The problem was that they also removed a similar looking line that was the path providing actual randomness.