ASL is not English, though. It has its own grammar structure and words (obviously) so it is functionally a different language than written English. People who speak ASL as a first language are essentially learning a second language with written English, one that is based on spoken language they can’t hear. As a result, many in the Deaf community struggle to read and write. Add to that the stress of it being an emergency and having to process the text in real-time before it disappears? I just don’t see captions being the answer for this already vulnerable community, especially in life-or-death situations.