Which are both the reasons why Biggin will never become a big commercial airport.
Some real nonsense being said here...
Biggin's problem is a planning restriction that they've been trying to overturn for some years, without success. They're not allowed to handle ticketed flights.
The transport options (lack of them) don't help, but if the desired aircraft can't get there in the first place, that's not the issue.
If they were taking EasyRyanJetAirs, it wouldn't be too much hassle to have a dedicated coach service to/from East Croydon, Orpington and Bromley South, from where the train services to Central London and other destinations are actually very good.
The service provided to GA at Biggin is nothing short of excellent. It's not much more than we pay elsewhere these days, landing fees are comparable to Shoreham, Redhill, Fairoaks, Southend, Blackbushe, Le Touquet and plenty of other popular GA destinations.