A few examples: using vmware fusion provides an option to enable nested virtualization
1) running a windows vm from macos, and inside that windows vm you enable and use WSL2 or docker desktop. Both of those windows tools require nested virtualization
2) run a hypervisor such as esxi or proxmox as the vm OS, which in turn launches vms. Handy for simulating infra.
3) run a macos vm and inside that vm, install docker desktop for mac
4) experiment with any qemu/kvm tooling inside a linux vm, such as multipass or kubevirt
Everything above is not possible on modern mac hardware but is on hackintosh
