Here are just some of the advantages of VM's.
In a single Host environment.
1. You build one template of a particular install Win7, Server 2016, Linux. Then you just clone it to a working computer in a matter of minutes.
2. Snapshot a computer, makes changes, and if you break it, just restore from the snapshot point of time.
3. Share resources such as CPU, memory and drive space.
4. Reduce power, hardware and space foot print.
5. Boot time is much faster
Multiple Host environment.
All of the above plus:-
1. Load balancing across Hosts.
2. Move a RUNNING guest from one Host to another if maintenance is required on a particular host.
3. Add extra physical drive space then assign it to a guest as required.
Note:- you still need licenses for each individual Guest you are running.