To my mind, the question asked in the Guardian article gets to the crux of the matter:
“Why would a political party, so close to an election, seek to stop people finding out what their policies are or their past voting record?”
Because enacted policy has become so divorced from the popularity contest of modern politics that even the people who vote for UKIP will feel appropriately self justified in rolling their eyes and muttering under their breath about the ‘bloody politicians’ who somehow subverted their Prom Queen guise prior to the election into the actual reality everyone else was trying to warn them about.