To be more specific: the current active fleet of hypervisors (xen, vmware..) is much younger on average than the current active fleet of traditional operating s

To be more specific: the current active fleet of hypervisors (xen, vmware..) is much younger on average than the current active fleet of traditional operating systems (bsd/linux/solaris). By "younger" I mean the source code was written, and the interfaces defined, much more recently.