"Need" being the important word here.
I do not need a Win8 VM, but for the cost of a gpu I can have a badass gaming pc more poweful than my ps4 inside my server.
I do not need an XBMCubuntu VM, but because I have one now, I no longer require a separate HTPC , so I can retire it.
I'm sure most people will be happy with docker, but the more I'm messing around with VM's the happier I am that they are being integrated.
Not to mention its cool as funk being able to tell ppl whats running on my PC when they ask
I love the idea of having One-PC-To-Rule-Them-All
Horse for courses though