The problem is that this niche is not stereotypically a very well paying niche. The intersection of high earners and disabled people is quite small (and the intersection between lowest 20% of income earners and disabled is quite large)n So, there's not really a lot of money (if any) to be made by focusing solely on this niche.
That's why the ADA and various government laws came into existence - nobody was catering to the niche since it wasn't lucrative enough.
That's why the ADA and various government laws came into existence - nobody was catering to the niche since it wasn't lucrative enough.