Accessibility features are used by people regardless of whether they have visual accessibility issues. For example, I (and many others–watch some WWDC presentations closely and you'll see this) use the "display zoom" feature during presentations and when doing UI work to focus on things. The feature where you wiggle the mouse cursor to make it big? That's an accessibility feature, but it got a prime spot at the keynote when it was announced. I have subtitles enabled all the time since it helps me catch things in videos if I miss what someone said. macOS has text-to-speech, which is quite useful to read me back things I write for grammatical errors or typos. Accessibility features can and are used by everyone. (Disclaimer: I have partial colorblindness and wear glasses.)

They could certainly take copywriting and proofing jobs.

Because it's already been mentioned a number of times in the thread and is a very major selling point (IMO).