i am not suggesting/asking about this because i believe deaf or the hard of hearing have difficulty typing. it seems to me that if we have speech recognition software, why not have actual gesture/hand-shape based language recognition software. that being said, there are numerous people who are much better communicators verbally than they are as typist, hence the still popular phone call apps on phones. Perhaps, there is a similiar percentage of communicators in ASL, or any other signed language, who are much better at communicating through their first language than through the keyboard interface. Fingerspelling words would at least be something that they are familiar on an fluent level and side step the intrusive typing interface.
from what i know of the deaf community, they have embraced technology such as ipads and iphones for exactly the reason you suggest, however these devices are still prohibitively costly for most of that community. yet, despite text messaging being clear and easy communication channels, i still get more Purple phone calls
from people in the deaf community than i get text messages.