How important is Web Accessibility?

Source: Dev.to

How important is Web Accessibility?

Since I learned web programming I always thought just like security is something we should never skip, I also think of web accessibility in the same regard for public sites, but I also try to always implement it on internal tools as well.

I am using this great tool from WAVE Web Accessibility Evaluation Tools (https://wave.webaim.org/). Does anyone else use it? I wonder if there are any alternatives that are better.