Walks are an indication of plate discipline. Swinging at hittable strikes is the key to good hitting. If a batter can control the zone and take advantage of forcing pitchers to "come in" you have a ballplayer on your hands.
The flip side of this is the "hope" guys. They hope to walk, they hope to hit the ball etc.
From a defensive perspective - a wild pitcher sucks the air out of a team. How many times to you see a pitcher go deep in counts and the team behind him starts standing up, spinning their heads etc. A couple of walks followed by defensive misplays has created more blowouts by far than a team stringing 5 or 6 hits together.