This is my favourite part of being a writer - reading. Ok, it can also give me a bit of angst about the quality of my writing, or lack of it, but mostly I enjoy it. If a person says to me, "I don't read", I honestly have no idea how to respond. That's like telling me they don't breathe.
A writer who doesn't read will not be a very good writer. I won't listen to any argument on that subject. Reading stimulates the imagination, the same imagination a writer relies on to come up with their own ideas. Reading also helps the writer to understand different aspects of writing, such as voice, characterisation and dialogue. It can help with grammar too.
It's important to read the genre that you write, although I like to read various others too. It helps to see the differences between genres, as well as the similarities. I don't just mean from a commercial point of view - understanding the market, etc - but from the point of development as a writer, too. I didn't really understand what genre my novels were until someone pointed me in the direction of similar books; I just wrote the stories that were in my head.
Basically, I just think you should read because, well, why wouldn't you want to?