Dumbledore is gay. Who cares?

Rowling has just recently revealed that Dumbledore is gay.  Sure, I’ve heard the name before, but I don’t know anything about the character because I don’t read the books.  Apparently he’s a well respected all-knowing gray bearded wizard.
Here’s my question: Who the hell cares?  I’m not sure why Rowling did this, and more importantly why [...]