Almost everybody is familiar with better resource utilization as one of the benefits of virtualization. You can reduce the physical footprint (have fewer physical pieces of hardware) and still run the same number of “standalone” servers as before virtualization.
I think however that there is another huge benefit that doesn’t get as much attention - virtualization allows you to eliminate physical human labor component from the process of provisioning, moving or decommissioning your servers (once the original hardware, where VMs will be running, is set up). What does it take to provision a new virtual server? Several commands - and you are done. What does it take to move a virtual server? Again, several commands - no need to hire a moving company. What does it take to decommission a virtual server? You guessed it - several commands. And all these commands can be put together into a script or a GUI, and the entire process of ordering hardware, receiving it, unpacking it, racking it, taking power to it (you also need to check if that power is available, by the way), setting up cooling for it, connecting it (cables are so old fashioned!) and then finally turning it on can be encapsulated in a relatively small piece of software.