Regardless of one's hobby, it can help improve flexibility. For runners, it improves leg flexibility. For all, it does improve flexibility of all joints, similar to the benefits of a chiropractor (possibly/ probably better).
Improvements for the mind.
This is an ideal list of plus points. In all activities, yoga helps the brain co-ordinate the body better (for runners, the legs!). That greater ability brings piece of mind. That can also be felt during a yoga session. Greater relaxation and happiness are the main benefits, both during and after a yoga session. I would present myself as a case in point.
The yoga teacher/trainer is an expert who can help every individual surprise himself (or herself). Mine has certainly helped me, and the same could be true for everyone who tries yoga.