When you see a button on a webpage, you probably know what it does. If you don’t, the page is poorly made. But just because you do, when you see it, doesn’t mean a disabled user does when interacting with it.
Are you new to frontend development and feel that all the popular libraries and frameworks are too daunting to get started with? Do you always balk at tutorials, when they mention installing a bunch of programs and libraries and running scripts, compilers, and bundlers when trying to learn something new?
Google is not infallible. Even they fail at following accessibility best-practices. I have found 3 examples of (very common) mistakes, that even the bright minds at Google and all their efforts and reviews failed to see before shipping them to end-users.