What is the virtualization server for?
The primary role of the virtualization server is to support in-context preview of Alfresco managed content. It is not, however, the only way to achieve this – the other options (along with a comparison between them) are described at WCM Preview. Note that the other functions the virtualization server has been used for in the past (including dynamic Web Form includes) have been superceded by non-virtualization-server based mechanisms that are recommended going forward. For that reason if you’re not using the virtualization server for in-context preview, it is redundant and should not be installed.