Why do people list sensory disabilities as just 'deaf/HOH' and blind/VI'?r?

I usually avoid trying to list disabilities, because the list will never be complete - so I ordinarily stick to categories of disabilities. Even that isn't completely accurate as many disabilities don't neatly fit into only one category. I sometimes lump hearing and visual disabilities into sensory, but sometimes list them separately (but then other sensory disabilities are left out.) There is no perfect solution - but I do get your point.