Complexity is also the enemy of security (and reliability). If the guy needs a file server, why should he be forced to use three OSes (bare metal and two VMs), a hypervisor, some virtualised networking between the VMs, and beefier (and therefore hotter) hardware to do it, when he could just use a puny box, one OS, and the firewall and file server directly within it? I guess someone thought that about FreeSWITCH (great feature!) at some point, too.
Just pointing out that there are two sides to the coin, and sometimes different answers for different needs.