I think you simplify the problem: cochlear implants are far from perfect and many users suffer from headaches while their hearing doesn't improve to the point that they can function like any other hearing person (eg typically they will have trouble discerning multiple voices speaking at the same time, hear anything in high background noise situations). So the choice for then is between being a disabled person in the hearing world, or a normal person in the smaller signing world. That's a hard choice, I'm glad I haven't had to make it. Sources: My linguist partner cooperates with many sign language researchers, so might be biased. But also, an acquaintance (also linguist) decided to not give their congenial deaf daughter a CI for this reason after considerable deliberation (please don't judge).