The KVM allows direct keyboard input and monitor display, as though you were at the machine,
in this instance imagine if you were doing some pretty major network reconfiguration to a
server, RDP/terminal services requires the network on the machine to be functional, similarly
ssh access to a linux server does.
The KVM allows you to work as though you're physically there (with a couple of exceptions) so
you can change bios settings, cancel that chkdsk on boot or even boot into safe mode, all of
which cannot be done through terminal services/rdp.
Obviously you're not there and can't press the reset button or a power button, however
there's IP connected power distribution units for that.