...which is part of the reason why you're seeing people in Linuxland rediscover things (LXC) the BSD community (Jails) have known for ages.
Why does everybody ignore the obvious explanation, that you'd get from the mouth of any participant, for a convoluted one that only fits the criterium of political correctness?
Having said that, please excuse my ignorance on system administration but, how does running a virtual machine that pretends to be a Linux/x64 box... on top of a real Linux/x64 box saves anybody at least some time? As a software developer who drank the Java kool-aid back in the 90, at least the "write once, run everywhere" mantra did make some kind of sense in those terms, but this other example is genuinely beyond me.
To me it has more to do with a tech company being able to put together an A-class team to serve a large number of customers that would not stand to pay the salary of a single full-time B-level IT guy if their business model depended on it.
To borrow someone else's words: https://blog.engineyard.com/2014/pets-vs-cattle
Or, in summary, it's a heck of a lot easier to instantiate a new instance of a machine from a snapshot than instantiate a new machine from a set of directions and some auto-config scripts.
I see some value in having a running system right now, instead of waiting for a long latency while the image is downloaded to real hardware... at least in some situations. However, is taking a permanent performance degradation of an order of magnitude worth that advantage?
By example, Moore Law has allowed us to pack incredibly large amounts to transistors in reasonably affordable machines, and what we do is... virtualization, a.k.a. write software that (presumably) simulates being a (much slower and limited) hardware system so a third party can run other programs on top of it, for a fee.
That kind of makes economic sense (because customers have a big appetite for computing power... just as long as they do not have to keep those pesky sysadmins on the payroll), but from a purely technological point of view is craziness. Every component you add into your stack is a potential source of error, and you do not gain any extra features because you are simulating real hardware... so, why to do it in the first place?
I think the answer is: because nobody would buy all those transistors if we didn't do so.