It think the lack of takers ,endorses BA's decision to pull the MAN route.
In its heyday LGW/MAN was one of the key routes feeding longhaul - thats when LGW was the sole UK gateway for ATL,DFW,IAH,LOS,TIP and these routes all had lots of connecting psgrs for MAN ,many of whom were high yielding.
These routes have all switched to LHR and LGW is left serving the 'Beach' routes to Florida,Caribbean plus DXB,LAS.
DXB,LAS , BGI have scheduled nontops from MAN .Charters serve other parts of the Caribbean, Florida and CUN.Large number of Florida and LasVegas bound psgrs connect in the US via the direct services to ATL,CLT,PHL.
Result is importance of MAN/LGW as a feeder is highly diminished in terms of numbers and yields from those remaining are not great.
The policy of GIP is to dis-courage small aircraft and their pricing means it is very difficult to make money with sub 100 seaters.A large proportion of the seats need to be filled just to pay for landing charges/turnaround handling charges ,leaving small scope to make any money.
Rising APD makes it difficult for airlines to raise fares to achieve profitability without making the total ticket cost unbearable.
In short theres more profit to be made using aircraft elsewhere although I do agree GIP will find it harder to attract new carriers without good connections to important cities like MAN.