If you develop for an audience where you do not know every of your end users, i.e for the generic public, i would argue you can never say it will not be used by

If you develop for an audience where you do not know every of your end users, i.e for the generic public, i would argue you can never say it will not be used by blind people (and hence have to develop for it). I was talking about app developers that build applications for jobs that require sight because of the nature of the job. Say a medical diagnostic application or airplane (simulator). You have to develop for the color blind, but for the completely blind, not so much. When selecting an UI toolkit I do not have to put that requirement up top.