Because in an OS like Linux or Windows, the kernel is sharing out access to the machine by managing the hardware's lowest levels of controls, which applications

Because in an OS like Linux or Windows, the kernel is sharing out access to the machine by managing the hardware's lowest levels of controls, which applications do not have access to. That's not even including the fact that processors are actually processor simulators these days. Thus, "bare metal" is actually "resource division among managed processes on a simulated processor" which sure sounds a lot like a VM to me. Modern OSs are in fact a form of virtual machine, and we found it useful to have yet another. Arguably docker type of simulation introduces yet another level so a react app in a docker shell in a VM cluster is really a interpreted application on a simulated operating system, on a resource sharing virtual machine, on a virtualized hardware environment, on a multitasking virtual machine, running on a simulated processor that's implemented on a _real processor_.