Elf slavery is surprisingly common, despite being a noble race of powerful spellcasters. One would think they have a degradation kink.
it's the classic scenario of the arms vs armor; if someone is physically strong, they require strong shackles accordingly; if a fictional universe contains a magic system, there must also be a means of restraining them, whether for legal or unlawful purposes; i would imagine shackles that drain magic reserves would be invented to that end