This is a role-playing item. Who doesn't want their character to have something that makes them stand out from the rest of the group. Whether you're a young rogue who lost their hand after getting caught stealing, a fighter who lost a leg in the war or a sorcerer who lost their arm when they first discovered their magical capabilities. This is something that is passive or that the DM can use to potentially make you more powerful giving the prosthetic its own magic capabilities as you progress.
