Pet Peeve

[Tiberius]

"dumb" isn't outdated slang; it's an outdated term for "mute", but the word is still in wide usage. More than that, I doubt many people say "deaf and mute"; most say "deaf and dumb".

[Darth]

If I may, I trained as a sign language (Auslan) interpreter (didn't pass though) and may be able to clear somethings up.

Deaf people, on average, have had a much worse education than hearing people (it's better now, but still very far from perfect). It's that their education has been woefully inadequate. Back in the past (still some now) a lot of schools would be totally oral, signing prohibited, and some would have their hands tied behind their backs for trying to point/gesture (but they would learn sign language on the playground and in their dorm rooms, back then most of the deaf education was at specialist schools for the deaf). How well do you think that worked? Just speaking at profoundly deaf kids. The kids who failed in the oral classes might be sent off to the signing classes (if they were lucky) but they had no language for the first important years of their life, they are still always going to be behind (and were now slowing down the signing class).

Don't get me wrong, there are deaf people who thrived and have gone on to uni and became lawyers and teachers and stuff, but it's rarer. Some deaf people's english is not at a level where captions are at all appropriate, especially when trying to give them emergency information*. We had the same thing happen when we had flooding in Queensland (and earthquakes in New Zealand), people were asking why on earth the politicians needed an interpreter next to them.

Edit: *Another thing which compounds the problem, look at the quality of 'live captioning' (compared to captioning that's been preprepared), some of it can be quite awful.