LTN can work for a lot of places outside of London...The major population centres of the East Midlands (Northampton, Leicester, Derby, Nottingham), plus a few decent-sized towns in-between, have no direct trains to any other airport (they're building the "EMA Parkway" station, but EMA is just a cargo hub with a couple of LCC flights thrown in). Similarly, car access is excellent with the M1 and M6 motorways, and a lot of regional roads to complement them. STN, OTOH, is right at the arse end of nowhere, offering just one road (which is not even a motorway, and which has traditionally been "enjoying" one of the highest road fatality rates in the country) and a slow regional train if you want to go anywhere outside London, restricting its catchment area to LON (loads of competition) and Cambridge (right next to STN, but rather small).

A possible LTN route by CO will by no means be a guaranteed success, but IMHO the comparison to STN just isn't valid...