Easier to mess with or reinstall OS remotely if you're not sitting in front of it, I'd imagine. Also can be easier to back up the whole system or take a snapshot of the system state, or nuke it and start over if you really screw it up.
I've dabbled with VMs for test environments but generally just install on bare metal.
I have about a dozen VMs running on a couple of large-ish servers (16 cores, 128 gigs RAM, 8 TB storage) Many of these are small, experimental environments (8 gigs RAM max, few hundred gigs storage) Running all those on metal would be expensive and annoying.
I've dabbled with VMs for test environments but generally just install on bare metal.