My guess: those who have a vested interest in "aiding" the blind would be damaged by something that frees the blind in any way. Most extreme case: suppose you created a "cure" for blindness. It would render all services for the blind obsolete. Don't you think the "industries for the blind" would do all they could to stop you?

It's the same reason there are maintenance drugs for such ailments as diabetes, HIV and herpes but no cures: the vested interests stand to make far, far more money with maintenance programs than with cures.