Because K's are not the end-all, be-all of pitching. They require a pitcher to throw more pitches, therefore limiting their innings, and when you have a shaky bullpen, that's not a good thing. Of the Tiger's pitchers, Fister is 54th in pitches per PA, and every other Tiger SP is 80th or worse (Scherzer at 80, Sanchez at 82, Porcello at 84, Verlander at 92). While K's may be an indicator of consistency, and might be a consistent 6 innings. In my opinion, you're just as well off having guys who produce ground balls, keep the ball in the park when they don't, and induce weak contact.