MS Cryptonet Cace and Metadata clean up

I noticed that I have the following setting on my WinXP system and the files in the cache and metadata folder are left alone by CCleaner:

C:\Documents and Settings\<user>\Application Data\Microsoft\CryptnetUrlCache\Content

C:\Documents and Settings\<user>\Application Data\Microsoft\CryptnetUrlCache\MetaData

Is there a reason for it?