It is part of the definition for intellectual disabilities though. From [1]:
> An individual is generally diagnosed as having an intellectual disability when: (1) the person's intellectual functioning level (IQ) is below 70-75; (2) the person has significant limitations in adaptive skill areas as expressed in conceptual, social, and practical skills; and (3) the disability originated before the age of 18. "Adaptive skill areas" refer to basic skills needed for everyday life. They include communication, self care, home living, social skills, leisure, health and safety, self direction, functional academics (reading, writing, basic math), and work.
Being bad enough at math that it impedes day to day life is not sufficient to qualify for intellectual disability under the ADA but it's one of the major factors.
I think the point is that even capable humans are often in situations where they are functionally disabled - like when they're really exhausted or inebriated or mentally/physically overloaded - and all of these accessibility technologies are helpful in those situations. It's not about the ADA definition but humans in practice.
[1] https://www.eeoc.gov/laws/guidance/persons-intellectual-disa...