I don't even know what you're trying to say. Stuttering is often irreversible, and wheelchair use is often reversible. Do you not realize that a lot of people that use wheelchairs do so after injuries that are treatable with surgery or physical therapy? My dad himself used to use a wheelchair and he doesn't need to anymore. In those cases like you mentioned, whispering or silent mouthing, how does "just talk" apply? "Just talk" implies talking normally, which neither of those cases are. My point is - how does saying "just talk" help anything?