Yes to avoid a mass PVR as everyone jumped ship and applied to Bristow for jobs.
But the process benefits everyone, not least the Govt, since peaks and troughs of availability of SAR service in the UK could be catastrophic; if there was a disaster in 2014/15 and the mil couldn't provide the aircraft and crews because so many had left and the new SAR service wasn't stood up in its place, the Govt would be asked why it contracted out SAR without a credible plan to cover contingencies.
As I said before - it has a lot to do with de-risking this contractorisation of SAR for the DfT.