Time to play devil's advocate here....
I work (very hard

) for a road haulage firm, which makes a tiny profit - profit margins of 1-3% of turnover are the norm now in transport. Why should my taxes then subsidise a competitor, which is aiming to take my firm's work off it and put me out of work?
Modal shift in the UK is firmly in pigs-might-fly territory - a combination of the small size of our island, and the lack of a proper rail network making most freight origin and destination points unable to be rail-linked have seen to that.
For example, my firm shift over a dozen loads a day, every day, from Wrexham to a site in the Forest of Dean. The goods are delivered to the destination on a just-in-time basis ready for a production line. If we were forced to use rail, we'd still need to road the goods out of our factory to a suitable railhead, and road them the other side from a railhead to the destination. We'd need to construct a big warehouse at the destination to take big loads, rather than delivering little and often as we do now. It just ain't gonna happen.
I firmly believe that most flows where rail makes sense are already using it - big heavy coal and steel flows, and non-urgent container moves. As such I believe the DFT was wasting its time and money trying to encourage new traffic.