Why can't the minimum price of alcohol be agreed upon?

Today the MSPs in the Scottish Parliament Health and Sport Committee debated the Government proposal to introduce a minimum price of 45p per unit of alcohol and voted to delete this proposal from the Bill (Parliament report not yet available). The Church, alongside medical organisations, the police and voluntary sector organisations have been campaigning in support of this policy  so I am disappointed to hear that opposition parties remain unwilling to compromise in order to make progress on this key public health issue. Everyone agrees that action should be taken to combat the excessive drinking culture in our nation, so what is preventing our representatives from sitting round the table together and agreeing what can be done, by this Scottish Parliament, in this piece of legislation?”