Why bother with accessibility. If a disabled wants to use an IDE, use a different one??
Disability isn't a permanent state that you start with. It's something that can happen to you 5 years into your career, or 15. It can also be temporary - you break your leg and now you need crutches, a cane or a wheelchair until you heal, for example.
Accessibility also helps people who you wouldn't traditionally classify as disabled: Designing UI to be usable one-handed is obviously good for people who have one hand, but some people may be temporarily or situationally one-handed. Not just because they broke an arm and it's in the cast, but perhaps they have to hold a baby in one arm, or their other hand is holding a grocery bag, or they're lying in bed on their side.
Closed captions in multimedia software or content are obviously helpful for the deaf, but people who are in a loud nightclub or on a loud construction site could also benefit from captions, even if their ears work fine.
So, ultimately: Why should someone who's used to using a given editor have to switch any time their circumstances change? The developers of the editor could just put the effort in to begin with.
If this were a simple, offline editor, a decision not to focus on accessibility would be far easier to swallow. They seem to be heavily promoting their collaboration feats. If those on your team collaborate using Zed and expect you to do the same, other tools aren't an option.
A11y isn't about helping one set of users (those who have completely lost their sight), it's about helping a whole spectrum of accessibility challenges - not by prescribing boxed solutions, but giving the user options customizable to their specific needs.
ramps (by parents with babies in their strollers), subtitles (by people learning languages or in loud environments), audio description (by truck drivers who want to watch Netflix but can't look at the screen), audiobooks (initially designed for the blind, later picked up by the mainstream market), OCR (same story), text-to-speech, speech-to-text and voice assistants (same story again), talking elevators (because it turns out they're actually convenient), accessibility labels on buttons (in end-to-end testing, because they change far less often than CSS classes), I could go on for hours.
For user interfaces specifically, programmatic access is also used by automation tools like Auto ID or Autohotkey, testing frameworks (there's no way to do end-to-end testing without this), and sometimes even scrapers and ad blockers.
If a programmer is using audio for feedback, then there is probably be some impedance mismatch by translating a visual interface into an audio description. Shouldn't there be much better audio encoding of the document? There would also be many more wasted cycles pushing around pixels, which the programmer will never see. An editor made specifically for visually impaired programmers, unencumbered by the constraints of a visual representation, would be able to explore the solution space much better than Zed.