HRC fuse is generally used for medium voltage circuits,what are the reasons for not using it in low voltage circuit.

Many low voltage circuits have fuses to protect the circuit from overloads. In answer to your question: It's the amperage that determines the type of fuse. A low voltage circuit with high amperage could use one, like on a ship. Small fuses to protect 24 volt control circuits in AC and heating units only need about a 1-2 amp fuse.