avast! Virus Cleaner was meant for big widespread infections; if you check the list of Cleaner-supported malware, you’ll see some big names that were on the top of the malware chart for a long time.
These days, however, you don’t see such kind of malware - one variant that would spread on an enormous number of computer. Instead, there’s an enormous amount of variants, each of them affecting only a few computers. This is not what avast! Virus Cleaner was built for… so I think it won’t be updated, unless a big “hit” appears again.