It makes no sense for a microservice that does one simple thing to run on top of 10 million lines of 90s C code. Especially since a lot of that code has to do with hardware quirks that don’t exist in a hypervised environment.
A hypervised environment also has 10 million lines of 90s C code with a lot of code dealing with hardware quirks, it is called the hypervisor.
You are right that it makes no sense to have a hypervisor, OS, and application. The hypervsior and OS are basically doing the same job. But the solution is not bare metal + hypervisor + device drivers + hypervisor services + library OS + application like a unikernel design. It is bare metal + OS + device drivers + OS services + application like a container design.
