Well there is, because they would not get public funds to do so. Both positions can spend up to £7M of campaign funds (which is not public money) during the campaign, and public funds cannot be spent during the ten weeks leading up to the referendum.
This is an additional £9M of additional public funding which the Government is using to publicise its position.
I will look forward to reading it - with a degree of scepticism, but I would also like to see the alternive view, in the same depth.