There's at least two clear incentives here. Losing the evidence means the hole in Smaug's armor is temporarily patched for when it flies in to Laketown. Secon

There's at least two clear incentives here. Losing the evidence means the hole in Smaug's armor is temporarily patched for when it flies in to Laketown. Secondly, losing the evidence means they get an innocuous selling point when they request a bigger budget to implement that arcane task of backing up files.