arm64 hardware is cheap, x64 hardware is cheap and both of those can run as many Linux or Windows VMs as you have RAM to run.
Why buy a second extra machine to do testing of multi machine infrastructure configurations when my workstation can run the VMs locally?
For others? I don't know that's why I think it's ridiculous to assume everyone else's use case is the same as your own.
arm64 hardware is cheap, x64 hardware is cheap and both of those can run as many Linux or Windows VMs as you have RAM to run.