I've heard of people who use hearing aids that have pretty good hearing when the hearing aids are in use that just get tired of using them and opt to be implanted.
Also, I am not sure if its this case with all deaf people, but many profoundly deaf people are able to use hearing aids now. Hearing aid technology has really advanced over the years. Marlee Matlin, the famous deaf actor, is profoundly deaf and she's able to use hearing aids. She is just one example though.
So I guess my question is, do hearing aids disqualify someone from being implanted or are hearing aids just another option as far as technology goes?