LHR is an hub airport LGW is point to point so long haul into/from LGW will only really work on routes where the vast majority of passengers are departing/arriving at their final destination. Should some like easyJet start long haul then given their huge short haul operation at LGW then it might become an easyJet hub.
Norwegians mini hub at LGW is only one dreamliner so its not statistically significant.