Yes, it is a graphical application, but there are various degrees of peoples abilities.

For example, we've been in communication with one person who uses Inkscape, but who has difficulty with the icons that can not go black-and-white. He gets quite a lot of use out of the application, but with just a little care on our interface side he ends up getting a lot more.

Then there are issues people have with reading, as opposed to actual vision problems. Screen readers are a big help there.

So overall, accessibility helps many people, for many different reasons.