The reason you never hear or see Demon Firesage, is he's a carbon copy of the Demon in the basement of Undead Asylum, which himself is just a slightly souped up version of the tutorial Demon boss, so, it's often not regarded as one of the most interesting bosses in the game. Also, it's sandwiched between Ceaseless Discharge and (redacted) Demon, who are both more mechanically interesting (if perhaps more annoying), so, less people see Firesage as a big milestone.
The reason you never hear or see Demon Firesage, is he's a carbon copy of the Demon in the basement of Undead Asylum, which himself is just a slightly souped up version of the tutorial Demon boss, so, it's often not regarded as one of the most interesting bosses in the game.
Also, it's sandwiched between Ceaseless Discharge and (redacted) Demon, who are both more mechanically interesting (if perhaps more annoying), so, less people see Firesage as a big milestone.