Delete or Put in Chest?

I'm running avast! and it has found several viruses, recommending putting these into a chest. I assume this is like a quarantine, but why not just delete the malware. Is there a risk that the virus could integrate further, or that the computer would think it has deleted it, but has not? Thanks!

The chest is basically quarantine. I guess it recommends that just in case it's a false positive. If you don't want to move it to the chest then just delete them instead.