It's also complicated by cultural factors. The culturally deaf (often written "Deaf") have their own culture -- sign language is a complete and distinct language, there are norms and practices unique to the culture. Acquiring the ability to hear is also the ability to, in effect, leave that culture and acquire the mainstream culture. Many Deaf people do not, in fact, view themselves as disabled or impaired. Particularly those who grew up mostly around Deaf people and who have an entirely Deaf experience in life. Everyone around them seems fine, they have their own distinct culture, etc.

As a consequence, getting an implant as an adult, or allowing your deaf newborn to be implanted, touches issues of social status and identity and politics within the Deaf community.

It doesn't take long for a culturally Deaf person to do a little thought experiment. What if the hearing can one day "solve" deafness in say 98% of children at birth? The cultural Deaf community may well face extinction under those circumstances. There would be no more children learning sign language as their native language, the chain of cultural transmission from deaf parent to deaf child would be broken. It is quite literally the end of their distinct culture and way of life, which they do not view as impaired or lesser.

You can even take this argument a step further. If mainstream society starts pushing and not simply offering cochlear implants to deaf children -- such as by creating a narrative that the Deaf are lesser or impaired in some way -- then that may well constitute a form of cultural genocide, taking the children of a particular culture judged as less or inferior, mutilating them, and forcing them to be raised in a different culture.

I'm not particularly convinced by the more extreme form of the argument, but it has been made, and the argument as a whole in all its various forms, I don't think can be fully dismissed easily. There is a point there.