[the_why_of_y]

The main practical benefit of C is the simplicity and stability of its ABI.

There are currently 8 different language bindings listed on LibVirt's website. It's not clear to me that this situation would improve by switching to a language as notoriously difficult to interop with as C++.

https://libvirt.org/bindings.html

[qalmakka]

The point is, C++ supports the C ABI. You can write your entire application in C++ and expose only a C-style API with the stable ABI you wish. I've done it a million times and it's absolutely fine.