Because those issues have left deep wounds in our society and we have historically ignored them. Just now we're allowing people from those groups into the discussion for the first time, and that is causing a lot of friction. Just look at the comment section of this article; the top comment in this comment section is someone willfully misrepresenting what the author of the article said, with a heavy implication that the author is stupid.

It's true that a lot of the programming can be clumsy or awkward. Sometimes, they get a little stuck talking about diversity and ignoring issues of class in a capitalist society, like in this article in which NPR talks about how we need more women Venture Capitalists. But overall, people talk about it a lot because we have a lot of talking about it left to do.