Manhunter had rather a lot of scary gay on panel and it didn't do that book's sales any good at all. It got them a few pats on the back, but the book still got canceled twice.
It's a fair point to make, that they could maybe expand their readership by broadening their demographic appeal, but the sales data doesn't seem to bear that out. What sells in superhero comics are A) huge crossovers, B) hot artists, and C) old franchises.
I'd argue that they've come a long way in demographic representation in even the last ten years, by introducing Billy, Teddy, Karolina, and Xavin, and allowing Northstar to be peacefully out of the closet nowadays. They're moving forward bit by bit, but looking at the sales data, I can't blame them for doing so extremely slowly.