What's lacking in sreeshanth?

He always impressed me every time touching 143 kmph he is a bowler who stood head to head with dale steyn who is the best bowler right now(remember the sa test series).Although being an inconsistent performer sree held his shoulders up when India needed him not always but some times.Allan Donald accounted that sree have genuine fast bowling skills and he can easily be a match winner.Coming to the present he is unpredictable considering the outings he had before the world cup I thought he might be the impact player of the same tournament but he surprised me he gone for 54 runs in five overs against a comparatively weak batting side.He got 2 or 3 overs right in WC final which included a delivery of 145.7 kmph but still he remained to be a liability to be the team conceding 52 runs in 8 overs.He showed the potential to be a good FAST bowler in him in numerous occasions.I want to know what is lacking in him and why he does not have a permanent place in Indian team? Clearly my question is why don't yet sree does not made an impact in World Arena??????