I believe that this is because what we want goes against the ideology of the EU federalist project. Some of them are still dreaming of the UK joining the Euro.
David Cameron was right to attempt a renegotiation. The hard-line Euro Sceptics would have rather we just threw in the towel and left. But finality is not the language of politics. So the approach Cameron has taken is both sensible and diplomatic. If we had merely had a referendum without renegotiation attempts it would have been diplomatically bad for Britain.
It looks like whatever is going to be offered is not going to be a substantial reason for us to remain within the undemocratic, federalist dictatorship that is the European Union. So I’m quite sure that I shall be voting to leave.