SF proper is terrible for most outdoors activities: you have to drive at the very least across the golden gate to do much of anything. Maybe it's ok for a Big City, but that's another reason why I wouldn't want to live in a Big City. I like outdoors activities, and don't like dealing with traffic just to participate in them.

Of course if you're comparing with 'back east', sure it's probably not so bad, but if you've ever lived in a place that's really good for outdoors sports, SF isn't all that great.