Why Would Iran Ever Want A Nuclear Weapon?

Let's see. George Bush puts you (Iran) in his 'Axis of Evil' along with Iraq and North Korea. Then George Bush attacks Iraq. Then he starts to go after North Korea, another member of his 'Axis'.

North Korea, however, tells George that it has nuclear weapons capability. George decides to leave that part of the 'Axis' alone.

Iraq. No nuclear capabilities. Attacked.

North Korea. Nuclear capabilities. No attack. Diplomacy and incentives instead.

I'll never understand why Iran feels it has to have a nuclear weapons capability.