The TV show See does a pretty good job of covering the why for this.
My understanding is that part of it is a “we’re not broken, we’re full people” along with “this is our culture” and the restoration of hearing is an erasure or something? I struggle to understand it myself and as a parent I would gladly lose my vision too if it meant restoring any healthy functioning for my son. It’s weird to me/
That said, I’m an outsider so I am only judging not understanding entirely.