The main advantages are that multiple OS can co-exist on the same computer in strong isolation from each other and tha it can provide an istruction set archtecture(ISA) different from that of the...
If I was designing a program for a computer that I do not have only a virtual machine would allow me to do that. That, as a programer, means I can not only design but test software for a mainframe...
In the UK the advantages can be mixed. There is a basic saving of 2 pence from the cost of a normal stamp and there is no need to queue up at a post office to buy the stamps in the first place....