Because not working on accessibility seems like a really bad idea. People really like to sue about these kinds of things, and accessibility is very important for many users (like me!).
"To Matt Mullenweg I want to say: please take better care of your community, because WordPress is nothing without it. Cherish the people who dedicate their (own) time and who work very hard to make WordPress the best it can be. Don’t ignore or make fun of them, but talk to them, guide them, inform them. Don’t be disconnected from the community, be part of it."
https://rianrietveld.com/2018/10/i-have-resigned-the-wordpre...