This developed because it couldn’t be fixed in our world, long enough for these people to develop communities, culture, and literally their own language.

In a world where it could always have been fixed, such communities and cultures are not likely to have ever developed, since the only people who could not get it fixed would be poor, and the poor are in a bad position to gather together in groups based on their shared experience and thus be able to form their own culture.

Furthermore, people not wanting to be cured today exist in a world where there already are significant accomodations for their disabilities. It is not likely these people would be able to do this if our society had not made the collective decision to put in the effort needed to accommodate disabilities.