Why A linear power supply's filter capacitors can hold a lethal charge long after the supply is unplugged. A bleeder resistor is connected permanently across the filter capacitor bank so that charge drains off through it when power is removed, typically bringing the voltage down to a safe level in seconds to a minute. It also helps stabilize the output voltage under light or no load, but its main job is safety.
Watch out Fusing against excess voltage is done by fuses, crowbar circuits or regulators, not by a resistor permanently in parallel with the capacitors. Ground loop problems are addressed by bonding and grounding practice, not by a bleeder.
Bleeder = bleeds the capacitors dry so the supply cannot bite you after you unplug it.