I think it’s just ignorance about alternate forms of communication and who might need them. It’s confusing for people to realize that some languages have no written form (sign) or that Braille isn’t an entirely separate language but a modified alphabet. Maybe people are just dumb too?

I can read braille (am sighted but learned in high school ‘for fun’, and now have a nephew who is blind that I write letters back and forth with) and am also conversational in sign language (not Deaf, just have lots of Deaf friends). I took an early interest in both, probably because I have Sensory and auditory processing difficulties and I was naturally drawn to forms of communication that process differently.

It's just straight ignorance. Our society doesn't really value disabled people (unless it's for inspiration purposes), so facts about our lives are not made readily available and our needs aren't given priority in public thought. Pretty sad too, cause lots of people could benefit from alternative commination options, not just disabled folks.