I know for a fact there are hearing impaired people on this forum.
As for the question, the person signing would have no use for the majority of deaf people. Believe it or not, most deaf people cannot sign. The more popular alternative nowadays is to have a cochlear implant or hearing aid (depending on the severity of the impairment). This allows the deaf person to hear. Of course this is the more popular option - why would deaf people choose not to hear?
The person signing will appear less and less as more people are implanted. However, the sound received by the bionic ears are not perfect at all, and there is quite a bit of interference - especially when watching the television. It is for that reason that many deaf people with bionic ears choose to have subtitles showing.
Very few people know how to sign. It's basically an outdated gimmick of deafness nowadays.