I recommend Christopher De Bellaigue's article in the Atlantic entitled "The Politics of Dignity: Why Nuclear negotiations with Iran keep failing".
Over and above any strategic value in having an ambiguous nuclear capability, Iranians tend to regard the ability to make decisions on their own soil and regarding their own resources as coterminous with national dignity. Mossadegh referred to the "moral" aspect of oil nationalisation; Tehran's rhetoric on the nuclear issue aims for a similar, high tone. There is broad agreement among ordinary people, whatever their feelings for the Islamic Republic, that the right to enrich uranium is not the West's to confer or withhold. The summer of 2009 saw huge protests against the Islamic Republic, but a Rand survey from 2010 found that 87 percent of Iranians support the civilian nuclear program, with 97 percent calling it a "national right." The West's rhetoric, as heard in Iran, has barely advanced from the old British contempt for Mossadegh. American and European officials reveal more than they intend when they speak of using "carrots and sticks" to change Iran's "behaviour" -- as if the countrywere a hormonal teenager.
I've written before about how this charade led by the US has actually tapped into a very strong Iranian national narrative of resistance to foreign domination. This of course should not be viewed as limited to Iran. Suppose the tables were turned, and the Iranians were the ones demanding that the US give up a sovereign right or else get bombed to heck. What would the reaction of an American be in that hypothetical case? Why assume that Iranians react any differently?