There are a whole raft of issues to confont:
Runway PCN; unless some re-surfacing has gone on lately it is shot.
Compliance with current DfT requirements for security (fencing for a start).
Then there is the issue of reliability; the Council ripped out the radar so only a non-precision approach aid is available. The runway is prone to surface icing in winter due to centreline drainage (hence its condition). These factors result in diversions (typically to Newcastle). Pretty soon the regular users of a scheduled service work out that they are better off driving the other way on the A69 and just using Newcastle.
For a viable, reliable service CAX needs a new runway (I understand that there are problems with the sub-strate - after all it was just 'floated' over moorland and bog at short notice for the Second World War) and lighting and an ILS. A single regional route would never repay that level of investment.