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.

That's reasonable, as long as a developer, once familiar with a toolkit like this one, doesn't go on to use it for applications with a less restricted audience.

There are a couple domains for which I'm pretty sure sight is required. Photoshop for instance. Is there any way this program could be made accessible?

For all the others, I wonder if a command line interface wouldn't just be better—sometimes not just for the blind.