Some? Every one that I’ve ever worked with, which is several hundred.
and why would IPMI port ranges and IP addresses be accessible outside of the DMZ, if you're an even half competent sysadmin?
If you are halfway competent, you do not use inband IPMI at all. IPMI belongs on a separate ethernet jack or at least a separate VLAN, connected only to a separate secured admin network. Which sysadmins can connect to, but which doesn't have connectivity to other parts of your network or the internet.
But I agree that you should filter all the relevant ports in all networks, just in case somebody screws up.