Yeah because he's good at playing in shit teams that build their entire gameplan around him. The results tend to stay shit just that he's scoring 60% of his teams goals and the football is terribad.
We already have 2 centre forwards that seem completely incompatible in a front 2, the last thing we need is another of the same ilk who can only function on his own. We need wingers, or flexible wide forwards, or a centreforward who can play back to goal, plus some new centre halves, plus a new fullback, plus a box-to-box midfielder... long before we need to sign Darren Bent.